State Kirchhoff's second law.

1. (a)State Kirchhoff's second law.[2]
2. (b)(i)1Two batteries, each of electromotive force (e.m.f.) 6.0 V and negligible internal resistance, are connected in series with three resistors, as shown in [Figure 5.1]. Resistor X has resistance 4.0 Ω and resistor Y has resistance 1.5 Ω. The resistance R of the variable resistor is changed until the voltmeter in the circuit reads zero. Calculate 1. the current I in the circuit,[1]
3. (b)(i)2Two batteries, each of electromotive force (e.m.f.) 6.0 V and negligible internal resistance, are connected in series with three resistors, as shown in [Figure 5.1]. Resistor X has resistance 4.0 Ω and resistor Y has resistance 1.5 Ω. The resistance R of the variable resistor is changed until the voltmeter in the circuit reads zero. Calculate 2. the resistance R.[2]
4. (b)(ii)Resistors X and Y are wires made from the same material. The diameter of the wire of X is twice the diameter of the wire of Y. Determine the ratio average drift speed of free electrons in X / average drift speed of free electrons in Y.[2]
5. (b)(iii)The resistance R of the variable resistor is now increased. State and explain the effect of the increase in R on the power transformed by each of the batteries.[3]

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