Alternating Current (Part 3)
41) What is the amount of power in AC circuit?
ANSWER) P = VI cosφ in a single phase network
where φ is the angular displacement between voltage and current.
42) What is power factor?
ANSWER) cosφ is called power factor. It is the cosine of phase difference between voltage and current in same circuit.
43) What is the power factor of an RL circuit?
ANSWER) PF= R/Z
44) What is apparent power?
ANSWER) It is product of voltage and current. Its units are VA, KVA.
45) What are components of apparent power?
ANSWER) It has two components; active power and reactive power.
Apparent power S = P + jQ
where S is apparent power, P is active and Q is reactive Power.
46) What is active power?
ANSWER) It is useful power which does useful work i.e. it produces heat, motive power and light.
47) What is reactive power?
ANSWER) It is a component of apparent power which is stored in the circuit in the form of magnetic energy or electrostatic energy. It is utilized to magnetize the cores of machines etc.
48) Name the parameter of an electric circuit which absorbs reactive power?
ANSWER) Inductance.
49) Name the parameter of an electric circuit which generates reactive power?
ANSWER) Capacitance.
50) Describe an important property of an inductance?
ANSWER) It does not allow sudden change of current through it.
51) Describe an important property of a capacitance?
ANSWER) It does not allow the sudden change of voltage, across it.
52) What is active power in three phase circuit?
ANSWER) P = √3VI cos φ
53) What is the impedance of an RL circuit?
ANSWER) Z = √(R2 + (WL2))
54) What is the impedance in RLC series circuit?
ANSWER) Z = √((R2+(WL-1/WC)2))
55) How active power is measured?
ANSWER) With the help of a wattmeter.
56) How active power is measured in three phase circuit?
ANSWER) Using one single wattmeter or by two wattmeter method or using a three phase wattmeter.
57) What are the units of active power?
ANSWER) Watt, Kilo Watt, Megawatt.
58) What are the units of reactive power?
ANSWER) VAR, KVAR, MVAR.
59) What are advantages of three phase supply?
ANSWER) Two voltages are available
i) voltage between lines and
ii) voltage between line and neutral.
More power can be transmitted using less conducting material.
Low line losses occur.
Three phase machines are self started.
60) How are the windings of a three phase machine connected?
ANSWER) Star or delta.
ANSWER) P = VI cosφ in a single phase network
where φ is the angular displacement between voltage and current.
42) What is power factor?
ANSWER) cosφ is called power factor. It is the cosine of phase difference between voltage and current in same circuit.
43) What is the power factor of an RL circuit?
ANSWER) PF= R/Z
44) What is apparent power?
ANSWER) It is product of voltage and current. Its units are VA, KVA.
45) What are components of apparent power?
ANSWER) It has two components; active power and reactive power.
Apparent power S = P + jQ
where S is apparent power, P is active and Q is reactive Power.
46) What is active power?
ANSWER) It is useful power which does useful work i.e. it produces heat, motive power and light.
47) What is reactive power?
ANSWER) It is a component of apparent power which is stored in the circuit in the form of magnetic energy or electrostatic energy. It is utilized to magnetize the cores of machines etc.
48) Name the parameter of an electric circuit which absorbs reactive power?
ANSWER) Inductance.
49) Name the parameter of an electric circuit which generates reactive power?
ANSWER) Capacitance.
50) Describe an important property of an inductance?
ANSWER) It does not allow sudden change of current through it.
51) Describe an important property of a capacitance?
ANSWER) It does not allow the sudden change of voltage, across it.
52) What is active power in three phase circuit?
ANSWER) P = √3VI cos φ
53) What is the impedance of an RL circuit?
ANSWER) Z = √(R2 + (WL2))
54) What is the impedance in RLC series circuit?
ANSWER) Z = √((R2+(WL-1/WC)2))
55) How active power is measured?
ANSWER) With the help of a wattmeter.
56) How active power is measured in three phase circuit?
ANSWER) Using one single wattmeter or by two wattmeter method or using a three phase wattmeter.
57) What are the units of active power?
ANSWER) Watt, Kilo Watt, Megawatt.
58) What are the units of reactive power?
ANSWER) VAR, KVAR, MVAR.
59) What are advantages of three phase supply?
ANSWER) Two voltages are available
i) voltage between lines and
ii) voltage between line and neutral.
More power can be transmitted using less conducting material.
Low line losses occur.
Three phase machines are self started.
60) How are the windings of a three phase machine connected?
ANSWER) Star or delta.
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