A Level physics electricity emf question

How can you tell whether there is internal resistance in a circuit? There is a question where the emf is 2.0V and there is only one component in the circuit (resistor). the potential difference across the terminals of the cell is 1.0v?

Ive figured there must be a 1.0v internal resistance- but is this because no charge can go back to the cell/ it must all be used? If not then why is it?

Reply 1

wannabe_lawyer

E = I(R+r), if there is no internal resistance then E = IR = V. Here you have V = 1 and E = 2 therefore there must be some internal resistance? (like you said 1v)