3. How many turns should a 14 cm long solenoid have if it is to generate a 0.875 mT magnetic field when 750 mA current is passed through it? (3 marks) 4. The magnitude of the magnetic field strength due to the Earth at a certain point is 68.5 ut. In order to generate a magnetic field as strong as this using a solenoid, with a current of 1.4 A passing through it, what should be the linear density of turns, n