The diagram below shows a circuit used to investigate one of the factors affecting resistance of a wire.

Three wires S, T and U of the same material, same thickness but with different lengths were used. Each wire was connected to the circuit between points P and Q at different times. Brightness of bulb: S — dim; T — bright; U — very dim.

1. aName instrument N. [1]
2. bHow many cells are there in the circuit? [1]
3. cArrange the wires S, T and U in the order of increasing resistance. [2]
4. dWhen each wire was connected it became warm after some time. State why the wires became warm. [1]
5. eWhich of the wires became warm fastest? [1]
6. fWhen wire T was connected, the readings from instruments N and O were 0.10 A and 12 V. Calculate the resistance of the wire. [2]

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