12.2 Potential Difference and Power Flashcards
What is the work done by an electron equal to
Its loss of energy.
What is the work done per unit charge defined as
Potential difference or voltage across the component
Potential difference is defined as…
…the work done (or energy transfer) per unit charge
What is the unit of pd
The volt
What is the volt equal to
1 joule per coulomb
If work W is done when charge Q flows through the component, the p.d. across the component V is given by…
V = W/Q
What is the emf of a source of electricity defined as
The electrical energy produced per unit charge passing through the source
What effect does an electric current have
A heating effect
A magnetic effect - used in electric motors and loudspeakers
In a device that has resistance such as an electrical heater, what is work done transferred as
Thermal energy
Happens because charge carriers repeatedly collide with atoms in the device and transfer energy to them so the atoms vibrate more and the resistor becomes hotter
In an electric motor turning at a constant speed, the work done on the motor is equal to…
…the energy transferred to the load and surroundings by the motor, so the kinetic energy of the motor remains constant.
Electric motors:
Charge carriers are electrons that need to be ______ ______ the spinning motor coil against ______ force on electrons dur to the motor’s ______ field
Forced through
Spinning
Opposing
Magnetic
For a loudspeaker, what is the work done transferred as
Sound energy
Electrons need to be forced through the wires of the vibrating loudspeaker coil against the force on them due to the loudspeaker magnet
Work done W =
IVΔt
Electrical power P =
IV
