A museum conservator uses a small solar-powered motor to turn a mirror that directs light from the sun onto a display case. Fig. 1 shows the motor. A coil i...
Question 1 Report
A museum conservator uses a small solar-powered motor to turn a mirror that directs light from the sun onto a display case. Fig. 1 shows the motor. A coil is fixed to an axle between the poles of two permanent magnets. The solar panel provides a potential difference of 6.0 V. Current enters the coil through carbon contacts. The split ring changes the connections to the coil after each half-turn, so that the mirror continues to rotate about its pivot.
(a) Name the parts labelled X and Y in Fig. 1. [2]
(b) Describe the energy transfer that takes place while the motor turns the mirror. [2]
(c) Explain why the coil experiences a turning effect when current flows through it. [3]
(d) Calculate the electrical power supplied to the motor when the current is 0.40 A. State the unit of your answer. [3]
Answer Details
(a) X is a carbon brush, and Y is a carbon brush. The brushes maintain electrical contact with the rotating split-ring commutator. [2]
(b) Electrical energy is transferred from the solar panel to the kinetic energy store of the rotating coil and mirror. [2]
(c) A current-carrying conductor in a magnetic field experiences a force. The currents in opposite sides of the coil are in opposite directions, so the forces on those sides act in opposite directions. These opposite forces form a couple, producing a turning effect about the axle. [3]
(d) Use \(P=VI\):
\[P=6.0\text{ V}\times0.40\text{ A}=2.4\text{ W}\]
The electrical power supplied is \(2.4\text{ W}\). [3]
Download The App On Google Playstore
Everything you need to excel in your exams
