Internal Resistance

definition for electromotive force

The change in electric potential energy per unit charge between two points, due to work being done on the charge, for example by a battery or a power supply

lost volts

The electric potential energy that’s lost per unit charge in a battery with an internal resistance

The combination of the e.m.f and the lost volts means that the difference in electric potential energy per unit charge between the terminals is V1​, where V1=e.m.f−lost volts

Terminal voltage

definition for terminal voltage

The potential difference between the terminals of a power source when the power source is connected by a complete circuit to a load (external) resistance

What is the terminal voltage is equal to if the power source is not connected by an external load through a complete circuit?

electromotive force

Identify the name of the resistors that are exterior to the power source

Load resistance

Identify the correct V-I graph for a circuit with internal resistance from the options below.

Correct answersYour answers

Internal Resistance

Resistance due to opposition of flow of charge within a source of e.m.f. 

: Lost volts

The difference between the terminal voltage and the e.m.f. of a source of e.m.f due to energy being dissipated across the internal resistance of the power source

Terminal potential difference / terminal voltage

The potential difference measured across the battery/power supply when that battery/power supply is connected by a complete circuit to a load (external) resistance. If there is no internal resistance, the terminal p.d. will equal to the e.m.f.

Potentiometer

A potential divider circuit which consists of one length of wire and a sliding connection to alter the ratios resistances of the two sections of wire

A student investigates the internal resistance of a power source. Which of these would you expect their V-I graph to look like??

A straight line sloping downwards from a positive y-intercept