Calculation of the electrical energy usage by electrical tool – problems and solutions

Calculation of the electrical energy usage by electrical tool – problems and solutions

1. In a house, there are 5 lamps 25 Watt used 14 hours per day, a 200 Watt refrigerator used 24 hours per day, and a 125 Watt water pump used 8 hours per day. How much electrical energy used for a month (30 days)?

Known :

Power of lamp = 5(25) = 125 Watt and time of use = 14 hours x 30 = 420 hours

Power of refrigerator = 200 Watt and time of use = 24 hours x 30 = 720 hours

Power of water pump = 125 Watt and time of use = 8 hours x 30 = 240 hours

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Types of electric charges – problems and solutions

Types of electric charges – problems and solutions

1. Based on the figure of the electric charges below.

Types of electric charge 1

Objects A and D are negatively charged (-), object A attract object B and repels object C, object D repels E. Determine type of electric charge of object B, C, and E.

A. Positive, Positive, Negative

B. Negative, Negative, Positive

C. Positive, Negative, Negative

D. Positive, Negative, Positive

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Nearsighted and farsighted – problems and solutions

Nearsighted and farsighted – problems and solutions

1. A child with nearsighted can read a book at a near point 1 meter. In order to read at a normal reading distance of 25 cm, determine the power of the lens must use by the child.

Solution :

The child suffers farsighted, where the near point of his eyes is 1 meter or 100 cm. The near point of the normal eye is 25 cm. The eye can normalize by a convex lens.

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