All flashcards topics

Potential dividersEdexcel A-Level Physics: Flashcards

What these 12 flashcards ask

  • State the potential divider equation.
  • Why is the supply p.d. shared in proportion to resistance in a series divider?
  • In a divider with a 3.0 kΩ and a 1.0 kΩ resistor across 8.0 V, what is the p.d. across the 1.0 kΩ resistor?
  • How does p.d. vary along a uniform wire carrying a current?
  • What effect does connecting a load across the output of a divider have?
  • Why must a voltmeter have a very high resistance?
  • Why does the resistance of an NTC thermistor fall as it warms?
  • How does the resistance of an LDR change as light intensity increases?
  • In a divider with an NTC thermistor and a fixed resistor, the output is across the fixed resistor. What happens to the output as temperature rises?
  • In the same circuit, what happens to the p.d. across the thermistor as temperature rises?
  • How do you choose a fixed resistor so a divider output is half the supply at a particular temperature?
  • What unit conversion is needed when finding the current in a divider with kΩ resistors?

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
See the full worksheet

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).