Flashcards
Internal Resistance and EMF
Cards in this deck (15)
- 1The symbol for EMF is...ε
- 2A circuit displaying internal resistance:
- 3EMF supplied is equal to...Terminal p.d (IR) + Internal p.d (Ir)
- 4An "r" represents...Internal resistance
- 5The equation for EMF is....ε = V + Ir
- 6Circuit we use to find EMF and internal resistance graphically :
- 7Method to find EMF and internal resistance graphically:1. Use variable resistor to change resistance, and record voltage and current for various resistances
2. Plot IV graph of results (will have equation V = ε - Ir ) - 8The gradient of the line V = ε - Ir tells us ...The internal resistance
(gradient is -r) - 9The Y-Intercept of the line V = ε - Ir tells us...The EMF
(Y-intercept is ε) - 10Is a circuit with an open switch reads p.d 6v , but with a closed switch it reads 5.8v , why are these different?When closed, a current flows through the battery, and a p.d develops across the internal resistance
- 11Open circuit = 6.0v Closed circuit = 5.8v Resistor = 10Ω Calculate internal resistance of batteryε = V + Ir
I = 5.8v / 10Ω = 0.58 A
EMF = 6v , P.D = 5.8v (Use IR to check)
6 = 5.8 + 0.58(r)
0.2 / 0.58 = r , r = 0.34Ω - 12What does internal resistance limit?Limits current
Wastes power / energy
Reduces terminal P.D - 13Potentiometer symbol:
- 14How does a Potentiometer work?We slide the cable down the side which splits resistance into 2 parts (may or may not be equal)
- 15EMF can be defined as.....Voltage when there is no current running (through a circuit)