Explain why a transformer only works with an alternating current and doesn't with a direct current.

A transformer is designed to step-up or step-down a voltage in a wire to make transferring electricity more efficient. To do this they contain two isolated coiled wires (of varied lengths depending on the transformer). The electromotive force (EMF) in the first (primary coil) drives an alternating current through the wire inducing a magnetic field. As the size and strength of a magnetic field is proportional to the current, the magnetic field constantly changes expanding and contracting as the current alternates.
The magnetic fields lines intersect the secondary coil of wire during the expansion and contraction, which causes the reverse to occur, where a magnetic field induces an EMF and current in the new wire without them being physically connected. As a direct current is constant, the magnetic field produced would not move and the field lines would not intersect the secondary wire resulting in no induction of EMF or current. Therefore only an alternating current works in a transformer.

Answered by Brendan W. Physics tutor

17804 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

Alex's rocket lands after 4.56s and Billy's lands after 5.21s. What was the initial (maximum) vertical velocity of both of their rockets as they left the launchpad to 3s.f.?


Initially, trucks A and B are travelling in opposite directions. A has mass 1000 kg and is travelling at speed 7ms^-1. B has mass 4000kg and is travelling at speed 2ms^-1. What is their speed and direction after collision if they move together?


Explain quantitatively how an object can follow circular motion whilst on a ramp with no friction in the radial direction.


How can we derive the 'suvat' equations of motion v=u+at and s=(u+v)t/2


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo
Cookie Preferences