A-level Physics (Advancing Physics)/Voltage/Worked Solutions

1. A battery has an EMF of 5V. What is the total potential difference across all the components in the circuit?

They are the same! The voltage decreases across the circuit from the voltage at one end of the battery to the other.

2. The voltages (relative to the voltage of the battery) on either side of a resistor are -6V and -5V. What is the potential difference across the resistor?

-5 - -6 = -5 + 6 = 1V

3. At a given point in a circuit, 5C of charge have 10 kJ of potential energy. What is the voltage at this point?

$V={\frac {10\times 10^{3}}{5}}=2{\mbox{ kV}}$

4. Why do the electrons move to a point 1 cm further along the wire?

The point further down the wire has a lower voltage (i.e. less energy per. coulomb) - the electrons will be at a lower potential energy at this point, and fall to it, just as objects fall to lower potential energies due to gravity.