A copper wire having resistance 0.01 ohm in each metre is used to wind a 400 turn solenoid of radius 1.0 cm and length 20 cm. Find the emf of a battery which when connected across the solenoid will cause a magnetic field of `(1.0 xx 10^-2)` T near the centre of the solenoid.

Explanation

To solve the problem, we will follow these steps:

### Step 1: Calculate the number of turns per unit length (n)
The total number of turns in the solenoid is given as 400, and the length of the solenoid is 20 cm (which is 0.2 m).

\[ n = \frac{\text{Total number of turns}}{\text{Length of solenoid}} = \frac{400}{0.2} = 2000 \, \text{turns/m} \]
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