E.m.f. And Internal Resistance Flashcards
What is load resistance (also called “external resistance)?
The total resistance of all the components in the external circuit.
What is internal resistance?
The resistance created in a power source when electrons collide with atoms inside the power source and lose energy.
What is emf?
Electromotive force. The amount of electrical energy a power supply transfers to each coulomb of charge.
What unit is emf measured in?
Volts.
What is the equation for calculating emf?
Emf = (electrical energy)/(charge)
What is the terminal potential difference?
The potential difference across the load resistance.
When does the terminal potential difference equal the electromotive force?
When there is no internal resistance.
What are “lost volts”?
The energy wasted per coulomb overcoming the internal resistance.
State the equation that relates electromotive force, load resistance, internal resistance and current.
Electromotive force = current(load resistance + internal resistance)
State the equation that relates electromotive force, terminal potential difference and lost volts.
Emf = terminal pd + lost volts
Why does a car battery need a low internal resistance?
To supply a large current.
What is the general internal resistance of a battery?
1 ohm.
