If a lamp converts 90% of electrical energy into useful energy, how much energy is wasted as heat when 200 J is supplied?

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Multiple Choice

If a lamp converts 90% of electrical energy into useful energy, how much energy is wasted as heat when 200 J is supplied?

Energy efficiency means only part of the electrical energy becomes useful energy; the rest is dissipated as heat. If 90% is useful, 10% is wasted as heat. With 200 J supplied, wasted energy = 0.10 × 200 J = 20 J. So 20 joules are wasted as heat (the lamp also produces 180 J of useful energy). The total still adds up to 200 J.

Energy efficiency means only part of the electrical energy becomes useful energy; the rest is dissipated as heat. If 90% is useful, 10% is wasted as heat. With 200 J supplied, wasted energy = 0.10 × 200 J = 20 J. So 20 joules are wasted as heat (the lamp also produces 180 J of useful energy). The total still adds up to 200 J.

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