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Magnetism and Electromagnetism
Quick questions on The magnetic effect of a current explained: O-Level Physics
7short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the field around a straight wire?Show answer
When a current flows in a straight wire, it produces a magnetic field made of concentric circles around the wire, lying in planes perpendicular to it. The field is stronger (circles closer together) near the wire and weaker further away. Reversing the current reverses the direction of the field.
What is the field of a solenoid?Show answer
A solenoid is a long coil of wire. When a current flows, the field inside is strong and uniform, running along the axis, and the field outside looks just like that of a bar magnet, with a north pole at one end and a south pole at the other.
What is the electromagnet?Show answer
An electromagnet is a solenoid wound around a soft iron core. The current produces a magnetic field, and the soft iron core greatly increases the strength because it becomes strongly magnetised. The key advantage is that the magnetism can be switched on and off with the current, and reversed by reversing the current.
What is making an electromagnet stronger?Show answer
The magnetic field of an electromagnet can be increased by:
What is q1?Show answer
Describe the magnetic field around a straight wire carrying a current. [2 marks]
What is q2?Show answer
State three ways to increase the strength of an electromagnet. [3 marks]
What is q3?Show answer
Explain why a scrapyard crane uses an electromagnet rather than a permanent magnet. [2 marks]
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