CBSE Guess > Papers > Question Papers > Class X > 2008 >Science > Science Theory

Sol. Size of the Object, h1 = + 2 cm
Object distance, u = – 40 cm
Image distance, v = + 40 cm (Real because it is obtained on the screen)
Focal length of the convex lens, f = ?
Size of the image, h2 =?
According to lens Formula

Q.15. (a) An electric bulb is rated as 50 W, 220 V. Calculate the energy consumed by the bulb in 20 minutes. Express your answer in commercial units of electric energy.
(b) Distinguish between overloading and short circuiting in a domestic circuit.
(c) Why is it essential to earth electrical appliances having metallic body?

Sol. (a) Power of the electric bulb = 50 W =kw
Time = 20 minutes =

Energy consumed = Power x time

=

(b) Overloading and short circuiting: See Q.2. (L.A.T.), Chapter 13

Science 2008 Question Papers Class X
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