An overhead power cable runs between two pylons. The length of the cable between the pylons is 250 m.
The current in the cable is 800 A.
The cable is in the Earth's magnetic field. The magnetic flux density of the Earth's magnetic field is 5.0×10−5 T5.0 \times 10^{-5}\ \text{T}5.0×10−5 T.
Assume that the cable is at right angles to the Earth's magnetic field.
Calculate the force on the cable due to the Earth's magnetic field.
Use the equation
F=B×I×lF = B \times I \times lF=B×I×l
The mass of the cable between the pylons is 300 kg.
Calculate the weight of the cable.
Use g=10 N/kgg = 10\ \text{N/kg}g=10 N/kg.
Calculate the force on the cable due to the Earth's magnetic field as a percentage of the weight of the cable.
The current in the cable is an alternating current with a frequency of 50 Hz.
Explain why the force on the cable due to the Earth's magnetic field changes direction 100 times every second.