Current (Edexcel GCSE Physics: Combined Science)

• Electric current is defined as the rate of flow charge
  • In other words, the size of an electric current is the amount of charge passing through a component per second

• The current, charge and time are related by the equation:

• Where:
  • I = current, measured in amperes (or amps, A)
  • Q = charge, measured in coulombs (C)
  • t = time, measured in seconds (s)

• The equation for current can be rearranged using the formula triangle below:

Charge, current, time formula triangle

• The wires in an electric circuit are made of metal, because metal is a good conductor of electric current
• In the wires, the current is a flow of electrons

In metal wires, the current is a flow of electrons. This image shows the electrons flowing through a lattice of metal ions

ANSWER:   B

Step 1: Write out the equation relating current, charge and time

Step 2: Rule out any obviously incorrect options

• • Option A does not mention time, so can be ruled out

Step 3: Try the rest of the options by applying the equation to determine the correct answer

• • Consider option B:

I = 4 ÷ 500 = 8 × 10^–3 = 8 mA

• • Consider option C:

I = 8 ÷ 100 = 80 × 10^–3 = 80 mA

• • Consider option D:

I = 1 ÷ 8 = 125 × 10^–3 = 125 mA

• • Therefore, the correct answer is B

• The amount of current flowing through a component is measured using an ammeter
• Ammeters should always be connected in series with the part of the circuit you wish to measure the current through

An ammeter can be used to measure the current around a circuit and always connected in series