Answer to Question 4 |

A solenoid of length 2.5 cm has 200 turns. A current of 1.65 A flows through it. Calculate the resulting magnetic field strength. Give your answer to an appropriate number of significant figures. |

The number of turns per metre = 200 turns ÷ 0.025 = 8000 turns per metre.
B = 4p
× 10 2 significant figures as the length is to 2 s.f. |