a. The diagram below shows a circuit containing a lamp and a variable resistor.

The circuit does not work. The lamp does not light and altering the setting on the variable resistor makes no difference. Re-draw the diagram, showing a circuit in which the variable resistor may be used to change the brightness of the lamp.

b. The diagram below shows two resistors and an ammeter connected in series to a 6 V DC supply. The resistance of the ammeter is so small that it can be ignored.

i. Calculate the combined resistance (in Ω) of the 8 Ω and 4 Ω resistors in series.

ii. I Calculate the current supplied by the 6 V DC supply.

II. State the value of the current..

..in section PQ of the circuit

..recorded by the ammeter

..in section SR of the circuit.

iii. Copy the diagram above, and show a voltmeter connected to measure the potential difference across the 4 Ω resistor.

Transcribed Image Text:

80 6 V A in