A certain step up transformer has a turn ratio equal to 20. This means that if t

Question

A certain step up transformer has a turn ratio equal to 20. This means that if the input is 5V AC, the output is 100 V AC. If the input is instead 5V DC, what is the output? A. 100V DC B. 100V AC C. 5V DC D. 5V AC E. 0V An object is placed 30 cm away from a diverging (concave) lens, whose focal length has an absolute value of 20 cm. Describe the image that is formed. A. Real, inverted, reduced B. Real, inverted, enlarged C. Virtual, inverted, reduced D. Virtual, upright, enlarged E. Virtual, upright, reduced

Explanation / Answer

1.ans: 0V (E)

working of transformer is based on the principle of mutual inductance. for that varying voltage or current is required

i,e emf induced in the secondary coil when varying current or voltage given to primary coil of transformer by forming magnetic flux through the core

E= -N (di/dt)

N is number of turns of coil

if we give 5V DC to primary side. for dc there is no change in voltage or current so output is 0V

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2) given object distance do = 30 cm

for divergence lens focal length f = -20 cm

lens equation is

1/di + 1/do = 1/f

1/di + 1/30 = 1/(-20)

1/di = (-1/20) - (1/30)

di = - 12 cm

magnification m = -di/ do = 12/30 = 0.4

.image distance is negative so image that formed is virtual and magnification is +ve so image is upright

ans is E) virtual , upright , reduced

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