Magnetism and the motor effect - Maths questions

Maths questions often start with the command words 'calculate' or 'determine'. They will then have a blank space for you to show your working. It is important that you show your working, don't just write the answer down. You might earn marks for your working even if you get the answer incorrect.

Some maths questions might ask you to 'show that' something is true. These questions often require you to prove something mathematically. For example, you might have to calculate two values and then compare them.

In some maths questions you will be required to give the units. This may earn you an additional mark. Don't forget to check whether you need to do this.

Maths questions might include graphs and tables as well as calculations. Don't forget to take a ruler and calculator.

If drawing graphs, make sure you:

  1. put the independent variable on the x-axis and the dependent variable on the y-axis
  2. construct regular scales for the axes
  3. label the axes appropriately
  4. plot each point accurately
  5. draw a straight or curved line of best fit (you can use a special best fit line ruler to help with this)

If you are asked to calculate an answer and it has lots of significant figures, you should try to round it to the same number of significant figures you were given in the data in the question. Don't forget to check your rounding.

There are no equations for this topic in Foundation tier.

Sample question 1 - Higher


A straight piece of wire is 0.713 m long.

It is placed at right angles to a uniform magnetic field of 0.47 T.

The force on the wire is 0.089 N.

Calculate the current in the wire.

Give your answer to an appropriate number of significant figures. [2 marks]

Edexcel question courtesy of Pearson Education Ltd.

I = \frac{F}{B~L}

I = \frac{0.089}{0.47 \times 0.713}

= 0.27~A

Use the formula sheet to find an equation which links force, current, magnetic field strength and length of wire. Rearrange this to make current the subject and then substitute in the numbers. Give your answer to two sf and include a unit. Two sf is appropriate since this is the smallest number of sf given to you in the values provided.