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Revision Sheet- Alternating Current
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Q1.The electric mains in the house are marked 220V, 50Hz. Write down the equation for
instantaneous voltage.
Q2. The instantaneous voltage from an AC source is given by E=300sin 314t. What is the RMS
voltage of the source?
Q3. At a very high frequency of ac, capacitor . Why?
Q4. Sketch a graph showing the variation of inductive reactance with frequency of the applied
voltage.
Q5. If the frequency of an ac source is doubled . What will be the new reactance of an
inductor?
Q6. How can an LCR circuit be made purely resistive?
Q7. In India domestic power supply is at 220V, 50Hz while in USA it is 110V, 50Hz. Give one
advantage and one disadvantages of 220V supply over 110V supply.
Q8. What is meant by capacitive reactance? What is the capacitive reactance of a capacitor
used in a circuit having DC emf? Explain.
Q9. A pure inductor is first put across 220V, 50Hz supplyand then across a 220V,100Hz supply.
Will the current drawn be the same or different in both cases? Explain.
Q10. A 15 microfarad is connected to 220V , 50Hz source. Find the capacitive reactance and
current in the circuit.
Q11. Why is the efficiency of an actual transformer is less than 100%?
Q12. 11kW of electric power can be transmiteed to a distant station at (i) 220V or (ii) 22kV.
Which of nthe two modes of transmission should be preferred and why?
Q13. Why is 220V AC more dangerous than 220V DC?
Q14. How transformer used in long distance transmission of electric power?
Q15. Explain why a capacitor blocks DC and allows AC to pass through it.
Naresh Sharma
8146624074
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