A spherical ball of radius 1cm coated with a metal having emissivity 0.3 is maintained at 1000 K temperature and suspended in a vacuum chamber whose walls are maintained at 300 K temperature. Find rate at which electrical energy is to be supplied to the ball to keep its temperature constant.

Explanation

To solve the problem of finding the rate at which electrical energy must be supplied to a spherical ball to maintain its temperature, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Parameters:**
- Radius of the spherical ball, \( r = 1 \, \text{cm} = 0.01 \, \text{m} \)
- Emissivity of the metal, \( e = 0.3 \)
- Temperature of the ball, \( T = 1000 \, \text{K} \)
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