The motor effect
A wire carrying a current creates a Area surrounding a magnet that can exert a force on magnetic materials.. This can interact with another magnetic field, causing a force that pushes the wire at right angles. This is called the The effect where a force is exerted on a wire carrying a current in a magnetic field..
Calculating the motor effect force
To calculate the force on a wire carrying a current at right angles to a magnetic field, use the equation:
force = magnetic flux density × current × length
\(F = B \ I \ l\)
This is when:
- F is force in newtons (N)
- B is magnetic flux density (magnetic field strength) in tesla (T)
- I is current in amperes - also referred to as amps - (A)
- \(l\) is length in metres (m)
Example
2 A flows through a 50 cm wire. Calculate the force acting on the wire when it is placed at right angles in a 0.4 T magnetic field.
50 cm = 50 ÷ 100 = 0.5 m
\(F = B \ I \ l\)
\(F = 0.4 \times 2 \times 0.5\)
\(Force = 0.4 \ N\)
Question
A 5.0 cm wire carries a current of 0.75 A. Calculate the force acting on the wire when it is placed at right angles in a 0.60 T magnetic field.
5.0 cm = 5 ÷ 100 = 0.050 m
\(F = B \ I \ l\)
\(F = 0.60 \times 0.75 \times 0.050\)
\(Force = 0.0225 \ N\)