NCEA LEVEL 1 PHYSICS
Electricity Quiz
Question One
The circuit shown has four identical ammeters. A2reads 0.2A and A3reads 0.3A
What would the current be through the other two ammeters?
They would both read the same value - and that would be 0.5A.
The sum of the 2 currents in the parallel pathways is equal to the current before it split (0.5A). When the pathways rejoin the current is again 0.5A. Current is NOT used up around a circuit.
Question Two
Which one of the following statements is correct?
- The resistance of P is more than 20 ohms.
- The resistance of P is equal to 20 ohms.
- The resistance of P is less than 20 ohms.
Give a reason for your choice.
The resistance of P is more than 20 ohms.
Since less current flows through A2 than A3, P has more resistance than 20 ohms.
(If they had been the same resistance then the current through each ammeter would have been the same. If P had had a lower resistance than 20 ohms then more current would have flowed through that pathway).
Question Three
Write down the equation that links current, potential difference and resistance.
V=IR where V is voltage or potential difference, I is current and R is resistance.
Question Four
Calculate the reading on the voltmeter. Show clearly how you work out your answer.
I=0.3A, R = 20 ohms
Since V=IR then V=0.3 x 20 = 6V
Question Five
State the potential difference of the power supply.
This would also be 6V.
Question Six
Calculate the resistance of resistor P. Show your working.
The voltage across P would also be 6V. The current through P is 0.2A.
V=IR so R=V/I. R=6/0.2 = 30 ohms.
(Look back at Q2. yes we said the resistance of P was > 20 ohms!)