𝐹 = 𝑙𝐼𝐵sin𝜃

• 𝐹 = 𝑙𝐼⊥𝐵 = 𝑙𝐼𝐵sin𝜃
  • conditions under which the maximum force is produced
• The relationship between the directions of the force, magnetic field strength and current
• Conditions under which no force is produced on the conductor

Learn.

It is important to refer to a wire as a current-carrying conductor – this is just preferred in HSC marking. Current-carrying conductor creates a magnetic field around it – this was discovered in 1820’s by Hans Christian Ørsted. This magnetic field can interact with other magnetic fields.

To determine the force acting on the wire we can use:

F = B I 𝑙 sin𝜃

• F : force acting on the wire (N)
• B : the magnetic field strength (T)
• I : the current in the wire (A)
• L : the length of the wire in the magnetic field (m)

Assumptions:

• The magnetic field is uniform
• There is no voltage drop in the wire

Using the right hand rule:

Memorize.

Master.

Question 1.

What is the force acting on the wire if the current running through the wire is 10 A, the wire is .1 m long and the angle the wire is to the 30 T magnetic field is 40 degrees? [2 marks]

Question 2.

What is the force acting on the wire if the voltage running through the wire of resistance of 3 ohms is 12 V, the wire is 25 cm long and the angle the wire is to the 3 kT magnetic field is 12 degrees? [3 marks]

Question 3.

The angle the wire is to the magnetic field if the current running through the wire is 10 A, the wire is .1 m long and the magnetic field strength is 30 T.

a) What angle will achieve maximum force? [1 mark]

b) What is the maximum possible force? [2 marks]

Answer.

1. 20 N
2. 623.7 N
3. a) 90 degrees (sin (90) = 1) | b) 30 N