Answer to Question 3 |

Short out the 80 ohm resistor:
Notice how the current flows:
We can work out the current from A to B:
I
I Total current = 0.875 A
Now remove the cells and short out the gaps. These cells have negligible internal resistance, so we don't have to worry about it.
These resistors are in parallel
R
R Here is the Norton Equivalent:
We haven't finished yet. We now put back the 80 ohm resistor:
Work out the parallel resistance:
R
R Now work out the voltage: V = 0.875 A × 18.46 W = 16.154 V = 16 V (2 s.f.) Now we can work out the current in the 80 ohm resistor: I = 16.154 V ÷ 80 W = 0.202 A = 0.20 A (2 s.f.) |