← All revision guidesSEMESTER 4 · DI04000181
6FLASHCARDSUtilization of Electrical Power
Heating, illumination, traction, welding and economical use of power.
Heating and welding
Q1State Joule's law of electric heating.
Heat produced is H = I²Rt joules when current I flows through resistance R for time t.
Q2Why is induction heating suitable for metals?
An alternating magnetic field produces eddy-current and hysteresis losses directly inside the workpiece.
Q3What is the basic principle of resistance welding?
Heat is produced at the joint by I²Rt loss while pressure holds the workpieces together.
Illumination and traction
Q1Define luminous efficacy.
It is luminous flux divided by electrical power input, expressed in lumens per watt.
Q2Why is regenerative braking useful in electric traction?
The traction motor operates as a generator and returns energy to the supply or battery while slowing the vehicle.
Q3What determines the tractive effort at the wheel?
Motor torque, gear ratio, transmission efficiency and wheel radius determine the force available at the wheel rim.