# Question 9

9.1 Learners investigated the relationship between potential difference (V) and current (I) for the combination of two resistors, R1 and R2. In one experiment, resistors R1 and R2 were connected in parallel. In a second experiment, resistors R1 and R2 were connected in series.

The learners then plotted graph X, the results of one of the experiments, and graph Y, the results of the other experiment, as shown below.

9.1.1 State Ohm’s law in words. (2)

9.1.2 What physical quantity does the gradient (slope) of the V-I graph represent? (1)

9.1.3 Calculate the gradient (slope) of graph X. (2)

9.1.4 Determine the resistance of resistor R1. (4)

9.2 The circuit below consists of three resistors, M, N and T, a battery with emf Ɛ and an internal resistance of 0,9 Ω. The effective resistance between points a and b in the circuit is 6 Ω. The resistance of resistor T is 1,5 Ω.

When switch S is closed, a high-resistance voltmeter, V1, across a and b reads 5 V.

Calculate the:

9.2.1 Current delivered by the battery (3)

9.2.2 Emf (Ɛ) of the battery (4) Voltmeter V2 reads 2,5 V when the switch is closed.

9.2.3 Write down the resistance of N. (No calculations required.)
Give a reason for the answer. (2)