A-LevelPhysicsD.C. circuits9702/21 · Oct/Nov 2017 · Q53 Marks
Three cells of electromotive forces (e.m.f.) E₁, E₂ and E₃ are connected into a circuit, as shown in Fig. 5.1. The circuit contains resistors of resistances R₁, R₂, R₃ and R₄. The currents in the different parts of the circuit are I₁, I₂ and I₃. The cells have negligible internal resistance. Use Kirchhoff's laws to state an equation relating [Figure 5.1]
- (a)I₁, I₂ and I₃,[1]
- (b)E₁, E₃, R₁, R₃, R₄, I₁ and I₃ in loop WXYZW,[1]
- (c)E₁, E₂, R₁, R₂, I₁ and I₂ in loop YZWY.[1]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.
- [B1] I₁ + I₂ = I₃ [any subject]
- [B1] E₁ + E₃ = I₁R₁ + I₃R₃ + I₃R₄ [any subject]
- [B1] E₁ - E₂ = I₁R₁ – I₂R₂ [any subject]
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