# Choppers – Exercise – 1

1. A step – down choppers can be used in :

(a) Electric traction
(b) Electric vehicles
(c) Machine tools
(d) All of these

Explanation
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2. Choppers is a :

(a) AC – DC converters
(b) AC – AC converters
(c) DC – AC converters
(d) DC – DC converters

Explanation
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3. The average value of the output voltage in a step – down dc chopper is given by :

(a) V0 = Vs
(b) V0 = DVs
(c) V0 = Vs/D
(d) V0 = Vs/(1-D)

Explanation
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4. A chopper operating at a fixed frequency is feeding an RL load. As the duty ratio of the chopper is increased from 25% to 75%, the ripple in the load current is :

(a) Remains constant
(b) Decreases, reaches a minimum at 50% duty ratio and then increases
(c) Increases, reaches a maximum at 50% duty ratio and then decreases
(d) Keeps on increasing as the duty ratio is increased

Explanation
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5. In dc choppers, the waveforms for input and output voltages are respectively :

(a) discontinuous, continuous
(b) continuous, discontinuous
(c) both continuous
(d) both discontinuous