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2 marksResistance, R

CSEC Physics · January 2015 · Paper 2 · Question 5(b)(i)

The brightness of the incandescent bulb in Figure 4 may be increased by varying the rheostat between 0 Ω and 100 Ω. When lit, the bulb operates at 0.30 A and 3.0 V.

What is the resistance of the bulb?

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Other parts of this question

  1. 5(a)(i)State the formula that relates the potential difference across a metallic conductor at constant temperature to the current through it.[1 mark]
  2. 5(a)(ii)State the formula that expresses the total resistance, R_T, of two resistors, R₁ and R₂, in parallel.[1 mark]
  3. 5(b)(ii)Assuming the resistance of the bulb remains constant once lit, calculate the ammeter reading if the rheostat is set to 100 Ω.[4 marks]
  4. 5(b)(iii)Is there a danger in reducing the rheostat resistance too much? Explain.[3 marks]
  5. 5(b)(iv)The assumption made in (b)(ii) is incorrect. With the aid of an I-V graph, indicate how the bulb's resistance actually varies with current.[4 marks]

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