Two long thin wires ABC and DEF are arranged as shown in Fig. They carry equal currents I as shown. The magnitude of the magnetic field at O is

Options

A. zero
B. `mu_0I//4pia`
C. `mu_0I//2pia`
D. `mu_0I//2sqrt2pia`

Answer

C

Explanation

(c) AB and DE do not give any magneitc field at O.
Magnetic field at O due to `BC=(mu_0I)/(4pia)`
It is directed 'up'
Magnetic field at O due to
`EF=(mu_0I)/(4pia)`, It is also directed up.
So, `B=(mu_0I)/(2pia)`