Review 4 Questions

A magnetic field forms because of the current flow. This magnetic field might be considered to expand and move out from the electromagnet. As the lines of force move out, the wire will cut them. This wire will therefore have current induced in it. If the electromagnet is disconnected from the battery, these lines of force will disappear and current will stop flowing in the wire. It can be seen now that current can be induced in a wire by three methods: 1. The wire can be moved through the stationary magnetic field (the principle applied in a dc generator). 2. The wire can be held stationary and the magnet can be moved so the field is carried past the wire (the principle applied in an ac generator). 3. The wire and electromagnet can both be held stationary and the current turned on and off to cause the magnetic field to build up and collapse so the magnetic field moves one way or the other across the wire (the principle applied in an ignition coil). REVIEW 4 QUESTIONS Q1. A magnetic field has what type of lines of force? Q2. When like magnetic poles are brought together, what action occurs? Q3. What are two parts of a basic electromagnet? 1-16