Abstract: A sleeve heater has an electrical and generally cylindrical heater coil centered on an axis and shaped to fit over a part to be heated, a radially compressible and generally cylindrical inner sleeve snugly coaxially surrounding the heater coil, and a radially generally inextensible and generally cylindrical outer sleeve fitted coaxially over the inner sleeve. The outer sleeve has an inner surface bearing tightly radially inward on the inner sleeve and radially compressing the inner sleeve and the coil inward. The inner sleeve is formed with two or more axially extending and axially oppositely open slots that are angularly equispaced, with alternate slots open axially in opposite directions.

Abstract: A heating jacket for use on a processing vessel includes a flexible heater jacket having a plurality of layers, a flexible heating element positioned within the layers, and a thermostat positioned within the layers and electrically connected to the heating element for regulating the heating element. An access opening is formed in at least one of the layers to provide access to the thermostat positioned within the layers. An access cover includes a pivotable inner cover which selectively covers the access opening and an outer cover which selectively covers the inner cover. A mounting bracket of the thermostat extends below a pair of parallel flexible strips to secure the thermostat to the layers whereby the thermostat is readily replaceable in the field.

Abstract: A housing is provided for maintaining a planar lightguide circuit at a temperature within a predetermined temperature range independent of ambient temperature. The housing includes a planar heating arrangement supporting and in thermal contact with the planar lightguide circuit. Also included is a frame assembly having a first surface on which the planar heating arrangement is fixed. The frame assembly has at least one opening through which extends at least one optical fiber coupled to the planar lightguide circuit. An overmold, which is molded around the frame assembly, includes at least one strain relief member through which the optical fiber extends.

Abstract: A low-voltage self-regulating heating device (200) for operation with supply voltages in the range of 0.1-12 volts having first and second layers (104, 106) of material, at least one of which is PTC material interposed between a first electrode (102) and a second electrode (108). Also a high-voltage self-regulating heating device (300) for operation with supply voltages above 240 volts having first and second layers (104, 106) of material, at least one of which is PTC material interposed between a first electrode (102) and a second electrode (108).

Abstract: While blowing out cooling air to a preform which is biaxially stretched and blow molded into a bottle shape, heat sources are made operative by a high power and the first heating process as quick heating is performed to the preform. Subsequently, the heated preform is left as it is and a temperature adjusting process to reduce a temperature difference between an outer surface temperature and an inner surface temperature of the preform to a predetermined value or less is executed. The second heating process to heat the preform until the outer surface temperature is equal to a temperature which is slightly lower than a crystallization temperature of the PET is executed to the preform obtained after completion of the temperature adjusting process while blowing out the cooling air to the preform. Thus, the quick heating of the preform is safely accomplished without causing an overheating state.

Abstract: A heater assembly for mounting around a fluid flow channel in an injection molding apparatus, the heater assembly comprising: an inner tube comprising a first heat conductive material having a first coefficient of thermal expansion, the inner tube having a selected longitudinal length, an inner surface, an outer surface; a first ring having an inner surface engaged around the outer surface of the inner tube along short selected length of the longitudinal length of the inner tube, the first ring comprising a second material having a second coefficient of thermal expansion that is less than the first coefficient of thermal expansion; a heater mechanism that heats the inner tube to a selected elevated temperature.

Abstract: A heated motorcycle handgrip is securable to a motorcycle handlebar and includes a grip housing that has a first end adapted to receive the handlebar, and a second end opposite the first end. The grip housing includes a heating element that is operable to provide a heat output, and a heater control dial is coupled to the second end of the handgrip to control the heat output of the heating element.

Abstract: A piping system that includes a plurality of pipe made of thermoplastic material, a coupling and an arrangement for securing the pipe to the coupling. The coupling is configured so that either a fusable seal or mechanical seal can be used with the coupling to connect the pipe to the coupling with an electrofusion joining control device. Preferably, the pipe and coupling are made of thermoplastic material.

Abstract: An electrically heating smoking system wherein tobacco smoke is generated by heating a portion of a cigarette with an electrical resistance heating element powered by lithium ion battery cells. The lithium ion battery cells supply current to the electrical resistance heating element with current up to 20 times greater than the recommended discharge rate. To prevent damage to the lithium ion battery cells under such high discharge conditions, the smoking system includes a controller which provides modulated pulses of electrical power from the battery cells to the resistance heating element during smoking of the cigarette.

Abstract: A heater device used for mold injection processes and related method for manufacturing the same is disclosed. The heater device comprises an inner sleeve having a hollow tubular body with opposed flanges formed at either end thereof and a resistive element applied around the body of the inner sleeve. In assembly, the inner sleeve is disposed inside and engaged to an outer sleeve having a hollow tubular body with opposed openings that communicate with a cavity defined between the inner and outer sleeves. The outer sleeve further defines a first aperture for permitting connection of terminal leads to the resistive element inside the outer sleeve during manufacturing. During manufacture, a slurry of ceramic insulation material is injected through a second aperture in order to completely fill the cavity and encase the resistive element.

Abstract: A liner for a branch pipe of an old repaired pipe lined with a polyethylene liner, the liner comprising: a branch pipe portion made of a tubular body, the branch pipe portion being insertable into an existing branch pipe branching from the old repaired pipe; a welding plate provided at a first end of the branch pipe portion, the welding plate having a top surface to be welded to an inner surface of the polyethylene liner and being formed to have a curvature corresponding the an inner surface of the old repaired pipe; at least one O-ring attached tightly to an outer circumferential surface of a second end of the branch pipe portion; an expandable pressing ring for pressing against an inner surface portion of the second end of the branch pipe portion adjacent to the O-ring to force the O-ring to form a watertight seal against the existing branch pipe; an expanding key for holding the pressing ring in an expanded position to maintain the pressure of the pressing ring against the second end of the branch pipe por

Abstract: Heating apparatus comprising a body of conducting material having oppositely directed surfaces extending between the edges, a channel formed one of the surfaces and defined by a pair of walls upstanding from the one surface, and a cover cooperating with the walls to define an enclosed passageway to receive a heating cable.

Abstract: An apparatus for encapsulating a connection of a pipe for transporting a fluid is provided. The apparatus includes a first section having at least one electrocoil surface operable to sealingly engage a surface of the pipe. The apparatus further includes a second section having at least one electrocoil surface operable to sealingly engage the surface of the pipe. The second section operably sealable to the first section to encapsulate a portion of the pipe and the connection of the pipe. The apparatus further includes at least one terminal mounted on at least one of the first and second sections. The terminal operable to energize the electrocoil surfaces of the first and second sections to electrofuse the electrocoil surfaces of the first and second sections to the surface of the pipe.

Abstract: A heating jacket for use on a processing vessel includes a flexible heater jacket having a plurality of layers, a flexible heating element positioned within the layers, and a thermostat positioned within the layers and electrically connected to the heating element for regulating the heating element. An access opening is formed in at least one of the layers to provide access to the thermostat positioned within the layers. An access cover includes a pivotable inner cover which selectively covers the access opening and an outer cover which selectively covers the inner cover. A mounting bracket of the thermostat extends below a pair of parallel flexible strips to secure the thermostat to the layers whereby the thermostat is readily replaceable in the field.

Abstract: In a method and apparatus for measuring the welding voltage at the heating coil of a heating coil fitting a welding current supply unit is connected to the connecting elements of the heating coil fitting by way of connecting lines and junction elements, and the welding voltage is detected by means of a voltage measurement unit. The welding voltage is detected at a respective contact of each of the two connecting elements of the heating coil fitting in electrically insulated relationship with respect to the connecting lines and the junction elements.

Abstract: A heater for fluids, the heater comprising a conduit having a wall and a surface, the conduit being configured to convey a fluid. In one arrangement, the conduit surface is roughened to mechanically secure a coating thereto. A conductor, configured to be electrically resistive and to extend over at least a portion of a roughened surface, and to adhere thereto throughout variations in operational temperatures thereof. The heater provides a clean, particle-free, non-reactive, non-trapping, ultra-pure, thermally tolerant, sealed system. The system maintains process fluids clean, even upon system failure, at contaminant levels below parts per billion, or even parts per trillion. In one arrangement, the heater comprises a quartz conduit with an electroless nickel plating of an engineered thickness on an external surface forming a resistive heater. The resistive heater conducts thermal energy through the wall of the conduit.

Abstract: A resistance element (19) for a device for shrinking shrinkable sleeves comprises an elongate electrical conductor extending in a zigzag pattern and bent to a tunnel shape. The shrinkable sleeve including for example an optical fiber enclosed therein is placed in that region of the resistance element (19), which corresponds to approximately the geometric axis of the upper semi-cylindric portion of the tunnel shape. The resistance element (1) has attachment pins (33) and contact and attachment pins (35) at its front and rear sides respectively intended to be placed in corresponding recesses in a lid of the device. The rear contact and attachment pins (35) have portions (39) intended for contact with elastic, electrically conducting contact pins with which the resistance element (19) comes in contact, when the lid is folded down to perform the shrinking operation.

Abstract: A fluid conduit has a peripheral wall defining a fluid passage extending along a longitudinal access. A heating element is located in contact with the peripheral wall and extending parallel to the longitudinal access. A jacket entrained about the peripheral wall and heating element maintains the heating element in contact with the peripheral wall.

Abstract: A low-voltage self-regulating heating device (200) for operation with supply voltages in the range of 0.1-12 volts having first and second layers (104, 106) of material, at least one of which is PTC material interposed between a first electrode (102) and a second electrode (108). Also a high-voltage self-regulating heating device (300) for operation with supply voltages above 240 volts having first and second layers (104, 106) of material, at least one of which is PTC material interposed between a first electrode (102) and a second electrode (108).

Abstract: An apparatus for aiding an individual using a plastic hose or pipe in an assembly or installation. The apparatus heats an end of the hose or pipe to soften the plastic, or other heat softenable material, thus making the end pliable, thereby allowing the hose or pipe to be more easily mated with a corresponding component. The apparatus is adapted for preventing the interior and/or exterior of the hose or pipe from deforming during the heating process.

Abstract: A heating sleeve for medical examination instruments includes an open circular band having a free end provided with a first engaging means and another free end provided with a second engaging means engageable with the first engaging means, a flexible heat emitting member affixed to an inner side of the open circular band, a power source mounted on an outer side of the open circular band, whereby the power source will heat the flexible heat emitting member thereby rapidly warning a contact member of a medical examination instrument and therefore preventing a patient from feeling uncomfortable to the cold contact member.

Abstract: A preformed heating element for use in a steering wheel including a heating element, embedded into a rubber or polyurethane material and preformed with manufacturing methods such as vacuum forming, resin impregnating, injection molding, and pultrusion progressive die.

Abstract: The present invention relates to heating trowel which processes by heat while observing the status of the working material, such as soldering iron, plastic welder, iron, hair iron and the like, and specifically it relates to heating trowel that could be used within few seconds from providing power. A heating trowel comprises a heating wire made of metal plate such as iron chrome alloy and which is thinned to the limit that it could maintain shape, an electrical insulator which is a thin plate of aluminum nitride and the like having more than 10 times the heat conductivity of said heating wire, and a trowel tip/heat storage made from copper and the like having more than twice the heat conductivity of the aluminum nitride and the like and also having high heat capacity, and formed by sufficiently adhering these components closely by pressing and the like using a heat insulating supporter.

Abstract: A temperature-controlled steering wheel for heating and cooling the user's hands while steering a vehicle. The temperature-controlled steering wheel includes a steering wheel member having an arcuate channel disposed therein; and also includes an arcuate outer tubular member being disposed in the endless channel of the steering wheel member; and further includes an arcuate inner tubular member being disposed in the endless channel of the steering wheel member and the outer tubular member; and also includes an assembly for heating the steering wheel member including a liquid being disposed in the inner tubular member.

Abstract: A method for regulating a coupling formation includes sensing a temperature of a coupling with a non-contact sensor and sending the temperature to a control unit that regulates the temperature of the coupling formation. In addition, a system for regulating a temperature of a coupling formation includes a temperature control unit and a non-contact sensor in flow communication with the temperature control unit.

Abstract: A heating element (10) having a first bus wire (12) and a second bus wire (14) and a plurality of flexible heating wires (16) which are connected between the first and second bus wires (12, 14), the flexible heating wires (16) which are connected between the within parallel zones (30), to make up modules (31), which may be attached together or cut to length so that the overall length of the heating element (10) may be varied thereby. The heating element may be self-regulating. Also a self- regulating regulating heating element (60) having a plurality of PTC heating elements (62) and at least one conductive pathway (68) which is interposed between two of the PTC heating elements, and forming a series circuit between said first and second bus wires (12, 14). Also a self-regulating heating device (100) having first and second layers (104, 106) of material, at least one of which is PTC material interposed between a first electrode (102) and a second electrode (108).

Abstract: An electrofusion joint assembly includes a meltable member, such as a pipe or fitting, and a heating element secured to the pipe or fitting. The pipe or fitting may be tapered to facilitate receiving another pipe to form an electrofusion weld joint. Fasteners are used to secure the heating element and extend through a meltable zone and into a non-melt zone. Power supplied to the pipe melts the pipe proximal the heating element.

Abstract: A method and apparatus for electrically heat welding a thermoplastic electrofusion fitting having an electrically resistive element disposed therein, whereby a regulated quantity of electric power is supplied to the resistive element during the welding process and the making of a high quality weld is ensured. In accordance with the method, electric power is supplied to the resistive element of the fitting. The resistance of the electrically resistive element is measured with low voltage electric power, and the size of the fitting to be welded is determined from a data table that can be loaded and modified by the user and sorted according to previously-fused fittings. The method includes the steps of generating a alternating current voltage from a direct current power supply and transmitting the alternating current voltage to the electrically resistive element.

Abstract: The invention relates to electrofusible units for pipe joints and other purposes able to avoid the employment of jointing equipment such as butt fusion equipment. The objective is met by an electrofusion unit comprising a length of elastomeric material with a winding of electrically conductive wire, the length of elastomeric material being notched to ensure that the wire winding is at a required spacing.

Abstract: A connecting clamp includes a heating member which surrounds a portion to be connected of a steel pipe and heats the portion to be connected, and a first clamp section and second clamp section positioned on opposite sides of the portion to be connected and clamping the steel pipe, whereby the portion to be connected is connected by heating the portion to be connected by the heating member while applying pressure to the portion to be connected by the first and second clamp sections. The first and second clamp sections and the heating member are so arranged as to be slid around the outer surface of the steel pipe from one side of the steel pipe to the other side thereof.

Abstract: A resistance element (19) for a device for shrinking shrinkable sleeves comprises an elongate electrical conductor extending in a zigzag pattern and bent to a tunnel shape. The shrinkable sleeve including for example an optical fiber enclosed therein is placed in that region of the resistance element (19), which corresponds to approximately the geometric axis of the upper semi-cylindric portion of the tunnel shape. The resistance element (1) has attachment pins (33) and contact and attachment pins (35) at its front and rear sides respectively intended to be placed in corresponding recesses in a lid of the device. The rear contact and attachment pins (35) have portions (39) intended for contact with elastic, electrically conducting contact pins with which the resistance element (19) comes in contact, when the lid is folded down to perform the shrinking operation.

Abstract: An electro-welding device for electrically welding plastic elements together, comprising: a power source for having an AC current in circulation, an electrical converter AC/DC, heating means electrically connected to the converter for heating the weldable elements, electrical regulating means interposed between the electrical converter and the heating means, the electrical regulating means comprising switching means having successive electrically passing and electrically non-passing phases, the electrical regulating means being subjected to the switch-over rhythm of said switching means for generating a switched over electrical signal.

Abstract: A thermal earmuff includes an inner cover having a circular partition formed with a first circular recess at one side thereof and a second circular recess at another side thereof, a circular member having two opposite circumferential edges provided with two curved shoulders and force-fitted within the second recess of the circular partition to support the inner cover, an outer side of the circular member being provided with a clamping device, a heating member secured on an outer side of the circular member and provided with a heating filament facing the through holes of the circular partition, an outer cover enclosing the inner cover, a head band having a plurality of teeth at two ends each of which is inserted into the slot with the teeth of the head band engaged with the teeth of the clip, and power supplying means electrically connected with the filament

Abstract: A heating element for heating a flexible intravenous tube includes a resistance heating wire having a pair of terminal ends encapsulated within an electrically insulating polymeric layer. The polymeric layer and the resistance heating wire are formed into a plurality of turns defining a coil having a central axis. Each turn of the coil is independently elastically expandable to surround a portion of the flexible intravenous tube when the intravenous tube is disposed axially through the coil such that the coil conforms to the shape of the flexible intravenous tube.

Abstract: A heating element assembly and a method of manufacturing heating assemblies. The heating assembly may be used for heating food products, including polypropylene bags containing cheese sauce or hot fudge, for example. The preferred heating assembly is configured to fit precisely around a standard cheese sauce bag, thus optimizing heat transfer between the heating assembly and the food product. The varied surface watt density of the heating assembly allows for accurate heat placement such that the food product can be efficiently and evenly warmed. A preferred embodiment of the heating element assembly includes two resistance heating elements. The first heating element is a temperature booster, while the second heating element is a maintenance heater to maintain heated food at a serving temperature.

Abstract: A heating element assembly and a method of manufacturing heating assemblies. The heating assembly may be used for heating food products, including polypropylene bags containing cheese sauce or hot fudge, for example. The preferred heating assembly is configured to fit precisely around a standard cheese sauce bag, thus optimizing heat transfer between the heating assembly and the food product. The varied surface watt density of the heating assembly allows for accurate heat placement such that the food product can be efficiently and evenly warmed. A preferred embodiment of the heating element assembly includes two resistance heating elements. The first heating element is a temperature booster, while the second heating element is a maintenance heater to maintain heated food at a serving temperature.

Abstract: An electric heating device includes a heating member, a closure unit and an electric wire unit. The heating member is formed as a flexible sheet with opposite first and second end portions. The heating member has upper and lower dielectric layers and an electric heating film layer which is disposed between the upper and lower dielectric layers and which generates heat when supplied with electric power. The closure unit is provided on the first and second end portions of the heating member for connecting the first and second end portions to each other so as to form the heating member into a tubular body and so as to retain a tubular shape of the heating member. The electric wire unit is connected electrically to the electric heating film layer, and is adapted to be connected electrically to an electric power source.

Abstract: A heating-element in a welding device for heating up plastic molded parts region by region during the welding operation is proposed, comprising at least two shell-shaped heating elements (2, 3) resting on the outside on the plastic molded parts in the region of the weld, the heating elements being of a rotationally symmetrical design, each heating element (2, 3) having a central region (7) and two edge regions (8, 9) arranged adjacently on both sides of the central region in the axial direction and designed in an axially symmetrical manner, and the edge region being formed from a material which has a lower thermal conductivity than the material of the central region.

Abstract: A dissolution testing system comprises a vessel plate on which a plurality of vessels are mounted. Each vessel includes a lateral wall having an outer surface around which a plurality of flexible heater elements are attached. Each heater element includes a transparent surface area, a heat conductive element extending along the transparent surface area, a temperature sensing element extending along the transparent surface area, and an electrical contact element connected to the heat conductive element and the temperature sensing element. The heater element can have more than one heating zone, with at least one of the heating zones being selectively energizable. The transparent heater element allows unobstructed view into the interior of its vessel, and reduces the time required to achieve a stabilized set point temperature in the vessel. A heater control system communicates with each heat conductive element and each temperature sensing element through a corresponding one of the electrical contact elements.

Abstract: A heater control system that utilizes electronic temperature control at each of a number of interconnected heaters is provided for monitoring and operating heaters within a narrow temperature range. In one embodiment, a heater control system is provided that is adapted for controlling a number of heaters positioned on pipe and components of a piping system from a remote location. The heater control system includes satellite controllers mounted on each heater connected daisy chain fashion and includes a monitoring station with a user interface for allowing a user to monitor and to remotely control the operating status or temperature of each heater in the heater control system. To satisfy the user's space requirements, the size of each controller is maintained at a small form factor and a single cord is used to provide power and communications lines to and between the controllers.

Abstract: A connecting clamp (4) comprises a heating member (9) which surrounds a portion to be connected of a steel pipe (1) and heats the portion to be connected, and a first clamp section (6) and a second clamp section (7) positioned on opposite sides of the portion to be connected and clamping the steel pipe, whereby the portion to be connected is connected by heating the portion to be connected by the heating member while applying pressure to the portion to be connected by the first and second clamp sections. The first and second clamp sections and the heating member are so arranged as to be slid around the outer surface of the steel pipe from one side of the steel pipe to the other side thereof.

Abstract: An improved water heater for use in spas, hot tubs, pools, hydrotherapy pools, bath tubs, and similar bodies of water used indoors, outdoors, or both indoors and outdoors are used for both therapeutic and recreational purposes. The water heater uses heating element technology know as thick film on substrate comprising resistive elements bonded to the outer dry surface of a substrate to heat the substrate which in turn heats the water flowing through the heating chamber. The heater is highly efficient due to the direct contact of the wet heating surface with the water and provides a smooth seamless inner heating surface by eliminating the need to pass electrical leads into the wet region of the heater. This virtually eliminates the risk of leaks in the water heater due to bulkhead fittings. The invention further eliminates the need for a heating element to be contained in the inner wet region of a spa heater, thereby reducing the risk of corrosion.

Abstract: A thermoweldable clip for a weldable conduit has two shells surrounding the conduit when in use. The shells have facing longitudinal flanges and are connected to one another under pressure. The shells have electrically heatable conductors arranged in continuous windings at inner shell surfaces. The windings extend in a semi-circular zone at the inner surfaces in two end areas of the shell and also between these two semi-circular zones in a planar strip. The shape and the arrangement of the conductors are identical. The shells are positioned so as to face one another. The strip is arranged only at the inner surface of one of the longitudinal flanges. Electrical terminals are formed integrally on the outer shell sides. The conductors project from the contact surface of the semi-circular zones or the strip on the longitudinal flange. A positive locking connection is provided between the conductors and the shell material.

Abstract: A method and system for ensuring that installations of fittings to plastic pipe meet governmental and/or industrial standards includes measuring physical parameters employed in the application of fittings to plastic pipe, recording the steps involved and values of the parameters measured, comparing the steps and values recorded for each installation with pre-established approved standards and providing a record identifying installations that meet or that do not meet pre-selected approved standards.

Abstract: A system and apparatus for and method of fusing a wrap to a portion of a length of plastic-coated pipe are disclosed. The system comprises a thermoplastic piece shaped to conform to the portion of pipe, the piece including a heat-generating trace and the heat-generating trace including a plurality of trace leads thereon. The system further comprises a clamp for applying pressure to the piece in the vicinity of the heat-generating trace, the clamp including at least two compression bands, each of the compression bands including a plurality of power leads, each of the power leads corresponding to one of the trace leads. The power leads preferably automatically are placed into electrical contact with said trace leads when the clamp is applied over the thermoplastic piece.

Abstract: A rebar end heating tool for heating cylindrically shaped pieces of rebar includes handle structure, and a heating unit. The heating unit is coupled with the handle structure and constructed with the capability of heating a piece of rebar having a diameter in the range of ⅜ inches to 1¼ inches to a temperature of about 500° F. in less than about ten seconds.

Abstract: Novel thermoplastic pipes which can withstand internally generated and/or applied pressures for utilization within, primarily, underground liquid and gas transport systems are provided. Such pipes are improvements over standard metal (i.e., steel, lead, and the like) pipes due to construction costs, shipping costs, implementation costs (particularly underground), flexibility (and thus modulus strength allowances) to compensate for underground movements (i.e., earthquakes and tremors), non-rusting characteristics, reduced crack propagation possibilities, and ease in manufacture. Such pipes are preferably reinforced with specific textile reinforcement materials that permit a lower thickness of plastic to be utilized than is generally required to withstand high pressure situations and also serve to prevent propagation of any cracks which may develop within the thermoplastic or thermoset materials.

Abstract: The invention concerns a device for preparing hydrocolloids comprising means heating a container containing a hydrocolloid. The heating means consist of preferably low-power ceramic resistors, insulated on three surfaces transmitting heat only through the top surface in direct contact with a tube square in external cross section and circular in internal cross section of diameter adapted to the diameter of the hydrocolloid cartridges.

Abstract: A preformed heating element for use in a steering wheel including a heating element, embedded into a rubber or polyurethane material and preformed with manufacturing methods such as vacuum forming, resin impregnating, injection molding, and pultrusion progressive die.

Abstract: A fluid control valve which comprises a valve body structure having a fluid flow passage therethrough and a first sealing surface means and a closure structure for controlling the fluid flow through the passage with the closure structure having a second sealing means adapted to engage the first sealing means to shut off fluid flow through the valve wherein there is formed in the valve body structure an annular groove proximate the first sealing means for the positioning therein of an electrical heater cable overlaid with a heat conductive layer, the heated cable extending into and out of the valve bodies so as not to interfere with the operation of the valve, the electrical heater cable in communication with a source of electrical energy.