A horizontal copper rod has a mass of 3.0 g.
A 5.0 cm length of the rod is in a uniform magnetic field. The rod is at right angles to the magnetic field.
The magnetic flux density is 0.40 T0.40\ \text{T}0.40 T.
The current in the rod is adjusted until the magnetic force on the rod acts upwards and is equal to the weight of the rod.
Calculate the weight of the rod.
Use g=10 N/kgg = 10\ \text{N/kg}g=10 N/kg.
Calculate the current needed for the magnetic force to be equal to the weight of the rod.
Use the equation
F=B×I×lF = B \times I \times lF=B×I×l
The current is increased to 2.5 A in the same direction.
Calculate the resultant force on the rod.
State the direction of the resultant force.
86 exam-style questions on Edexcel GCSE Physics 12.3 The motor effect, covering 12.3.1 The motor effect, 12.3.2 Fleming's left-hand rule, 12.3.3 Force on a conductor, and 12.3.4 Electric motors. Each one has a worked solution and a mark scheme showing where the marks go.