12.2 Potential Difference And Power Flashcards
What do electrons do as they travel through a circuit with a bulb
Electrons deliver the chemical energy from the battery which is turned into thermal energy as it passes through the bulb
After delivering energy to the bulb each electron reenters the battery through the positive terminal to be re supplied with more energy to deliver to the bulb each electron
When does the battery have the potential to transfer energy from its chemical store
If the battery isn’t part of a complete circuit
What happens to the energy when a battery is in a complete circuit
Each electron passing through a circuit component does work to pass through it and therefore transfers some or all of its energy
What is work done by an electron equal to
It’s loss of energy
Definition of potential difference
The work done per unit charge
Or
Voltage across the component
What is 1 volt equal to
One joule per coulomb
Potential difference =
W/Q
Work done over unit charge
What is work done also referred to as
Energy transferred
What is the emf source of electricity defined as
The electrical energy produced per unit charge passing through the source
What is the unit for EMF
Volts
What is the electrical energy produced when q passes through the source for a source of EMF
=Qe
What happened to the energy produced by EMF
It is transferred to other parts of the circuit and some may be dissipated in the source itself due to the sources internal resistance
When does a electric current have a heating effect
When it passes through a component with resistance
It also has a magnetic effect with the use of electric motors and loudspeakers
What happens in a device that has resistance eg an electrical heater
The work done on the device is transferred as thermal energy
This happens because the charge carriers repeatedly collide with atom in the device and transfer energy to them so the atoms vibrate more and the resistor becomes hotter
On an electric motor turning at a constant speed what is the work done on the motor equal to
The energy transferred to the load and the surrounding by the motor
so the kinetic energy of the motor remains constant
The charge carriers are electrons that need to be forced through the wires of the spurning motor coils against the opposing force on the electrons due to the motors magnetic field
What is the work done on a loudspeaker transferred as
Sound energy
Electrons need to be forced through the wires of the vibrating loudspeaker coil against the force in them due to the loud speaker magnet
Work done w =
IV delta t
Power equals energy over time therefore
Electrical power (P) = IV
What is the unit for power
Watts w
What is one volt equal to
One watt per ampere
when to use potential difference or emf
potential different is within the circuit
emf is in the source of the potential difference
unit for work done
joules
