Internal resistance
- Every component has internal resistance.
- E is the EMF of the cell/battery.
- V is the potential difference across the terminals.
- r is the internal resistance of the cell/battery.
Equation
E=Ir+V = Ir + IR = I(r+R)
Example calculations
If a battery has an internal resistance of 3\Omega and an EMF of 9V, what is the current flowing and terminal p.d. when it’s connected to a load of 12\Omega?
- r=3
- R=(12+3)=15
- E=9
- I=\frac9{15}
- V=0.6*12=7.2
- E=3
- V=2.8
- R=8
- I=2.8\div8=0.35
- $
| Question | Answer |
|---|
| What is the internal resistance of every component? | Every component has internal resistance. |
| What does E represent in the context of internal resistance? | E is the EMF of the cell/battery. |
| What does V represent in the context of internal resistance? | V is the potential difference across the terminals. |
| What does r represent in the context of internal resistance? | r is the internal resistance of the cell/battery. |
| Give the equation that relates EMF (E), terminal p.d. (V), current (I), and internal resistance (r). | E=Ir+V = Ir + IR = I(r+R) |
| A battery has internal resistance 3\Omega and EMF 9V, connected to a load of 12\Omega. How do you calculate the current flowing? | I=\frac9{15} |
| A battery has internal resistance 3\Omega and EMF 9V, connected to a load of 12\Omega. How do you calculate the terminal p.d.? | V=0.6*12=7.2 |