Voltage, emf and power Flashcards
(17 cards)
What is potential difference?
the energy transferred per unit charge when electrical energy is converted into another form of energy
Units: JC-1 or V
What is electromotive force?
the energy transferred per unit charge when another form of energy is converted into electrical energy
Units: JC-1 or V
Components in circuits eg bulbs, resistors convert
electrical energy into other forms eg light, heat
When there is a pd energy is …
lost
When there is an emf energy is …
gained
What is power?
the rate of energy transfer
What is Kirchhoff’s Second Law?
the sum of the emfs around any loop in a circuit is equal to the sum of the pds around the loop
Which conservation law does Kirchhoff’s second law relate to?
Conservation of energy
Current in series…
is constant
Current in parallel…
adds up
Voltage in series…
adds up
Voltage in parallel…
is constant
An emf can be produced by…
electromagnetic induction in a generator or by the chemical reactions in a cell
All sources of emf have…
an internal resistance
Internal resistance results in
energy being lost as heat when the battery produces a current
What is terminal pd?
voltage across the terminals of the power supply (will be less than emf because of pd across internal resistance)
Maximum power is provided when:
R=r
External resistance = internal resistance
