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Energy and voltage in circuits

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Question 50

An adaptor plugged into the mains supply is used to charge a smart-watch. The diagram shows the adaptor displaying the voltage and current readings as the battery charges. An adaptor connected via a cable to a mains supply on the left and a smart-watch charging dock on the top. The digital display on the adaptor shows: '0.32 A' with a label 'A' beside it, representing the current reading; and '4.80 V' with a label 'V' beside it, representing the voltage reading.

a.

State the equation linking voltage, current, and resistance.

[1]
b.

Use the readings on the adaptor to calculate the resistance of the circuit used to charge the battery. Give the unit.

[3]
c.

The battery of the smart-watch takes 90 minutes90\text{ minutes}90 minutes to charge. The charging current is 0.32 A.

State the equation linking charge, current, and time.

[1]
d.

Calculate the charge transferred to the battery.

[2]
e.

The cable connecting the smart-watch to the adaptor is replaced with a much thinner cable of the same length and material. Explain how this would affect the time taken for the battery to charge (assume the same total charge is transferred to the battery).

[3]

Energy and voltage in circuits Questions

  1. IGCSE
  2. /Physics
  3. /Energy and voltage in circuits