Force on a wire
Electromagnetism - OCR A-Level Physics
Worked Example
A wire of length 0.15 m carries a currentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A). of 4.0 A at an angle of 30° to a uniform magnetic field of flux densityMass per unit volume of a material. Measured in kg m⁻³. 0.080 T. Calculate the force on the wire.
Show Solution
1
Identify known values
$B = 0.080 T, I = 4.0\;\text{A}, L = 0.15\;\text{m}, \theta = 30°.$
2
Apply F = BIL sin θ = 0.080 × 4.0 × 0.15 × sin 30°.
3
sin 30° = 0.5.
4
$F = 0.080 \times 4.0 \times 0.15 \times 0.5 = 0.024 N.$
5
Direction
use Fleming's left-hand rule with the component of the wire perpendicular to B.
Answer
$F = 0.024 N = 24\;\text{m}N.$