E.m.f and Internal Resistance

Batteries have resistance.

• Resistance comes from electrons collliding with atoms and losing energy.
• In a battery, chemical energy is used to make electrons move. When they move, they collide with atoms inside the battery.
• This resistance is internal resistance!
• Internal resistance is what makes cells warm up.

• The amount of electrical energy the battery produces per unit charge is called the electromotive force (e.m.f)
• The p.d. across the resistance of the components in the circuit is called the terminal p.d.
• If there was no internal resistance, the terminal p.d. would be the same as the e.m.f. However, in real power supplies there is ALWAYS energy lost overcoming internal resistance.
• Energy wasted overcoming internal resistance is called lost volts.

Many calculations about e.m.f and internal resistance.

One equation interpereted…