Question

A student claims that if lightning strikes a metal flagpole, the force exerted by the earth’s magnetic field on the current in the pole can be large enough to bend it. Typical lightning currents are of the order of${\mathbf{10}}^{\mathbf{4}}$to${\mathbf{10}}^{\mathbf{5}}$ A. Is the student’s opinion justified? Explain your reasoning

Short answer

No, the student’s opinion that the lighting current are of the order${10}^4$ and${10}^5$ is not justified

Step-by-step solution

Magnetic field

Magnetic force is the force of attraction or repulsion arising between an electrically charged particles as a result of their motion.

Now, Magnetic field due to current carrying wire is given by:

$F=ILB\sin \theta$

Calculating the force

We know that the magnetic field is given by:

$F=ILB$.

Assuming the pole length is 10m, we get:

$$\begin{gathered} F={10}^5\left(10\right)\left({10}^{-5}\right) \\ =10N \end{gathered}$$

As the result is very strong, it will depend on the material of the flag post. Hence the student might be right on the material of the pole.