Question:

An electric motor runs on DC source of emf $200 \,V$ and draws a current of $10\, A$. If the efficiency be $40\%$, then the resistance of armature is

Updated On: Jun 23, 2023
  • $ 2\,\Omega $
  • $ 8\,\Omega $
  • $ 12\,\Omega $
  • $ 16\,\Omega $
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The Correct Option is C

Solution and Explanation

Input power $ =VI=200\times 10 $ $ =2000W $ Output power $ =\frac{40}{100}\times 2000=800W $ Power loss in heating the armature $ =2000-800 $ $ =1200W $ $ \therefore $ $ {{I}^{2}}R=1200 $ or $ R=\frac{1200}{{{I}^{2}}} $ $ =\frac{1200}{10\times 10} $ or $ R=12\,\Omega $
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Notes on Current electricity

Concepts Used:

Current Electricity

Current electricity is defined as the flow of electrons from one section of the circuit to another.

Types of Current Electricity

There are two types of current electricity as follows:

Direct Current

The current electricity whose direction remains the same is known as direct current. Direct current is defined by the constant flow of electrons from a region of high electron density to a region of low electron density. DC is used in many household appliances and applications that involve a battery.

Alternating Current

The current electricity that is bidirectional and keeps changing the direction of the charge flow is known as alternating current. The bi-directionality is caused by a sinusoidally varying current and voltage that reverses directions, creating a periodic back-and-forth motion for the current. The electrical outlets at our homes and industries are supplied with alternating current.