Tag: electric power

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Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

If the length of filament of a heater is reduced by  10%, the power of the heater will 

  1. increase by about 9%

  2. increase by about 11%

  3. increase by about 19%

  4. increase by about 10%
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$P=\dfrac { { V }^{ 2 } }{ R } \ R=\dfrac { \rho l }{ A } \ \therefore P=\dfrac { { V }^{ 2 }A }{ \rho l } $

$ \therefore P\alpha \dfrac { 1 }{ l } \quad $ [Keep in $\dfrac{v^2A}{\rho }$ constant]
$\therefore$ with reduction of $l$ by $10\%$ power will increase by $10\%$.

Multiple choice physics electric current and circuit domestic electric circuits and safety precautions domestic and commercial circuit electric power

The wire having a red plastic covering is a 

  1. live wire

  2. neutral wire

  3. earth wire

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

During wiring in our houses , we use the traditional concept of using red color wire as live , black as neutral and green for earth. These color codes are used to distinguish between live, neutral and earth wires, which is a standard coding of color nowadays.

Multiple choice physics electric current and circuit domestic electric circuits and safety precautions domestic and commercial circuit electric power

The wire having a black plastic covering is a

  1. live wire

  2. neutral wire

  3. earth wire

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

During wiring in our houses , we use the traditional concept of using red color wire as live , black as neutral and green for earth.These color codes are used to distinguish between live, neutral and earth. which is a standard way of coding of colors for electric connections.