Fig. 9.1 is a circuit diagram. The electromotive force (e.m.f.) of the battery is 12V.

1. (a)Explain what is meant by electromotive force.[2]
2. (b)(i)1.State the relationship between the current Iβ in the battery, the current I₁ in the 18Ω resistor and the current I₂ in the 30Ω resistor.[1]
3. (b)(i)2.State an equation that relates the e.m.f. E of the battery, the potential difference V₁ across the 18Ω resistor and the potential difference V₂ across the 30Ω resistor.[1]
4. (b)(ii)Calculate the current in the battery.[2]
5. (b)(iii)Calculate the potential difference (p.d.) across the 18Ω resistor.[1]
6. (b)(iv)Calculate the power produced in the 18Ω resistor.[2]
7. (c)The resistors obey Ohm's law. State Ohm's law and describe one limitation on this law.[2]
8. (d)(i)The resistors are made from the same material, but have different cross-sectional areas and different lengths. State the relationship between (i) the resistance R and the length l of a wire of constant cross-sectional area,[1]
9. (d)(ii)the resistance R and the cross-sectional area A of a wire of constant length.[1]
10. (e)A resistor is shown in Fig. 9.2 and part of the resistor colour code is shown in Fig. 9.3. State the colour of the bands on the 30Ω resistor.[2]

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