A technician calibrates a current balance used in a satellite laboratory. Fig. 1 shows a straight wire of length 0.080 m in a uniform magnetic field. The cu...
Question 1 Report
A technician calibrates a current balance used in a satellite laboratory. Fig. 1 shows a straight wire of length 0.080 m in a uniform magnetic field. The current is 3.0 A. The balance measures a magnetic force of 0.12 N on the wire.
(a) Calculate the magnetic flux density of the field.
Use the equation: force = magnetic flux density × current × length. [3]
(b) Which direction is the magnetic field in Fig. 1? [1]
(c) Give one change that would double the force on the wire. [1]
(d) Describe why there is no force if the wire is parallel to the magnetic field. [1]
Answer Details
The motor-effect equation applies when the wire is perpendicular to the magnetic field.
- (a) \[F=BIL\]
\[0.12=B\times3.0\times0.080\]
\[B=\frac{0.12}{0.24}=0.50\ \text{T}\] [3] - (b) The magnetic field is from N to S, so it is left to right. [1]
- (c) Doubling the current, the wire length in the field, or the flux density doubles the force. [1]
- (d) The motor-effect force is zero when current is parallel to the magnetic field. [1]
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