Question

If a 50W lamp is lit for for 2 hours, the amount of electrical energy converted into heat and light
is [ ]
a) 3.6 × 105
J b) 3.6 × 10–5 J c) 3.6 × 104
J d) 3.6 × 10–4 J

Answer 1

Given

P = Power of lamp = 50 W

t = Time the lamp is on for = 2 hours

To find

The amount of electrical energy converted into heat and light

Solution

E = Energy converted to heat and light

Power is given by

$P=\dfrac{E}{t}\\\Rightarrow E=Pt\\\Rightarrow E=50\times 2\times 60\times 60\\\Rightarrow E=360000=3.6\times 10^5\ \text{J}$

The amount of electrical energy converted into heat and light is a) $3.6\times 10^5\ \text{J}$.

Answer 2

Explanation:

P=50W LAMPS LITS

T=2HRS =2×60×60

NEEDED

ENERGY CONVERTED TO HEAT AND LIGHT

P=E/T

E = PT

E =50×2×60×60

E = 360000

E = 3.6×10*5

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