B. block DC voltage from the speaker transformer. C. provide positive feedback.

Question

B. block DC voltage from the speaker transformer. C. provide positive feedback. D. prevent transistor damage from a shorted speaker. 15. A DC amplifier will amplify signals down to a low-frequency limit of A. 1,000 Hz. B. 0 Hz. C. 100 Hz. D. 10 Hz. + 12V R32 C1 L INPUT Rs 8 SPEAKE 16. For the amplifier circuit shown in figure above, which of the following statements correctly describes the way transistor 22 is connected? A. The emitter of 22 is common to both imput and output. B. The base of 02 is common to both input and output. C. The input and output signals of 02 are 180 degrees out of phase. D. The input and output signals of O2 are in phase. 17. What is the purpose of connecting a diode across the winding of a DC-operated relay? A. To maintain constant DC drop across the relay B. To eliminate relay chatter C. To increase relay magnetic pull D. To soak up inductive kick 18. The primary-to-secondary turns ratio of a certain transformer is 1:5. If the AC voltage across the primary is 100 V, what would be the value of the AC voltage across the secondary winding? A. 500 V B. 550 V C. 680 V

Explanation / Answer

15) Answer - Option (B) is correct.

Explanation - A zero frequency type amplifiers are used to amplify steady voltages or currents whose frequency range extends down to zero frequency.

16) Answer - Option (A) and Option (C) both are correct.

Explanation - From the figure given we can easily find that output is taken from the emitter terminal of transistor Q2. and this terminal also common between input of Q2 and Output of Q2 so this transistors emitter is common between input and output of Q2.

By proving this transistor Q2 in common emitter configuration now we know that if a transistor is in common emitter configuration the phase difference between input and output is 180 degrees. So the input and output signals of Q2 are 180 degrees out of phase.

17) Answer - Option (D) is correct.

Explanation - Voltage equation of inductor is V = L (di/dt).

And we know that inductors do not allow sudden change in current but when we switch off the supply across the inductor the voltage across the inductor Spikes up due to the sudden change in current and due to the property of the inductor it tries to keep the current constant and hence pulls more charge which leads to the high voltage spikes this is called inductive kick. This is very dangerous for semiconductor circuits or other elements and hence a diode is used across it in the the opposite direction of normal current flow to soak up inductive kick.

18) Answer - option (A) is correct.

Explanation - As we know that in a transformer primary to secondary turn ratio is equal to primary to secondary voltage ratio.

i.e N1/N2 = V1/V2 --------------(1)

Given that primary to secondary turn ratio N1/N2 = 1/5

And Voltage across primary is (V1)=100 V

So From equation (1)

N1/N2 = V1/V2

1/5 = 100/V2

So V2 = 100*5 =500 V

Hence voltage across secondary winding is 500 V.

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