Physics 9702 · AS & A Level · Force on a current-carrying conductor
Force on a current-carrying conductor — practice question
As shown in Fig. 9.1, a stiff wire is supported horizontally between the poles of a magnet. When a constant current of $6.0\,\text{A}$ flows through the wire, the magnet experiences an extra downward force of $0.080\,\text{N}$.
(a)[3]
On Fig. 9.1, draw an arrow on the wire to indicate the current’s direction. Explain your answer.
(b)[4]
The steady current of $6.0\,\text{A}$ is replaced by a low-frequency sinusoidal current. Its root-mean-square (r.m.s.) value is $2.5\,\text{A}$. Calculate the difference between the greatest and smallest forces now acting on the magnet.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “wire is subjected to an upward force by Newton’s third law” …