Calculating Electric Energy (Edexcel GCSE Physics)

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Calculating Electric Energy

  • Work is done when charge flows through a circuit
    • Work done is equal to the energy transferred

  • The amount of energy transferred by electrical work in a component (or appliance) depends upon:
    • The current, I
    • The potential difference, V
    • The amount of time the component is used for, t

  • When charge flows through a resistor, for example, the energy transferred is what makes the resistor hot
  • The energy transferred can be calculated using the equation:

E = P × t

  • Where:
    • E = energy transferred in joules (J)
    • P = power in watts (W)
    • = time in seconds (s)

  • Since P = IV, this equation can also be written as:

E = I × V × t

  • Where:
    • I = current in amperes (A)
    • V = potential difference in volts (V)

  • When charge flows around a circuit for a given time, the energy supplied by the battery is equal to the energy transferred to all the components in the circuit

Worked example

Calculate the energy transferred in 1 minute when a current of 0.7 A passes through a potential difference of 4 V.

Step 1: Write down the known quantities

    • Time, t = 1 minute = 60 s
    • Current, I = 0.7 A
    • Potential difference, V = 4 V

Step 2: Write down the relevant equation

E = I × V × t

Step 3: Substitute in the values

E = 0.7 × 4 × 60 = 168 J

Examiner Tip

'Energy transferred' and 'work done' are often used interchangeably in equations, don't panic, they mean the same thing!Always remember that the time t in the above equations must always be converted into seconds

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Katie M

Author: Katie M

Expertise: Physics

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.