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Unit 4 Fields and their Applications
Quick questions on Magnetic fields: the motor effect and force on a moving charge - WJEC A-Level Physics
5short 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 motor effect?Show answer
A current-carrying conductor in a magnetic field feels a force, the motor effect, where is the angle between the current and the field. The force is maximum when they are perpendicular () and zero when parallel (the conductor then lies along the field and cuts no field lines).
What is force on a moving charge?Show answer
The two force expressions are consistent: a current is simply moving charge, and summed over all the carriers gives per charge.
What is fleming's left-hand rule?Show answer
Use the left-hand rule for the force on a current (or the conventional current direction of a positive charge): the thumb gives the force (motion), the first finger the field, and the second finger the current.
What is q1?Show answer
A wire carries perpendicular to a field. Find the force on it. [2 marks]
What is q2?Show answer
Explain why the magnetic force on a moving charge does no work on it. [2 marks]
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