Potential dividersEdexcel A-Level Physics: Mind map

Exam questions on Potential dividers

1. A potential divider is made from a 12 V battery of negligible internal resistance, a 4.0 kΩ resistor R₁ and a 2.0 kΩ resistor R₂ connected in series. R₁ is joined to the positive terminal and R₂ to the negative terminal. The output p.d. is taken across R₂.
   A load of resistance 2.0 kΩ is now connected across R₂. Calculate the new output p.d.2 marks
2. A garden light switches on automatically at dusk. A 5.0 V supply of negligible internal resistance is connected across a 10 kΩ fixed resistor in series with a light-dependent resistor (LDR). The output p.d. is taken across the fixed resistor, and the lamp is switched on when this output falls below 2.0 V. The LDR has a resistance of 2.0 kΩ in daylight and 40 kΩ in the dark.
   Explain why the output p.d. falls when it gets dark.2 marks
3. A uniform resistance wire PQ of length 1.00 m and resistance 20 Ω is connected across a 6.0 V cell of negligible internal resistance. A sliding contact J is placed on the wire at a distance of 0.35 m from Q, and the output p.d. is taken between Q and J.
   Calculate the output p.d. between Q and J when nothing else is connected to the circuit.3 marks