(i) State and define SI unit of power.

(ii) A person carrying 10 bricks each of mass 2.5 kg on his head moves to a height 20 m in 50 s. Calculate power spent in carrying bricks of the person. (Given, g = 10 ${{ms}^{-2}}$)

# State and define SI unit of power

(i) Power The rate of doing work is called power. Its SI unit is watt.

(ii) Given, mass of one brick = 2.5 kg Mass of 10 bricks = 2.5 X 10 = 25 kg Height, h = 20 m, time, t = 50 s, power, P = ?

Power = mgh / t = 25 x 10 x 20 /50 = 100 ${{Js}^{-1}}$

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Resistance is the hindrance offered by an object to the flow of current through it. Lower is the flow of current, higher is the resistance of a given material.

SI unit of resistance is Ohm (Ω). It is resistance offered by an object when 1 volt potential difference is applied across it and 1 Ampere of current passes through it.