Select Board & Class
equation of alternating current is given by I = 10(2)1/2sin(100piet + pie/6). the time taken by current to reach the root mean square value from t=0 is t1 then the value of t1 is
1) 1/1200s
2) 1/250s
3) 1/200s
4) 1/800s
in an oscillating L-C circuit , the maximum charge on the capacitor is Q. the charge on the capacitor , when the energy is stored equally between the electric and magnetic field is
1) Q/2
2) Q/(2)1/2
3) Q/(3)1/2
4) Q/3
a coil has resistance 30ohm and inductive reactance 20ohm at 50Hz frequency . if an AC source ,of 200V , 100Hz is connected across the coil, the current in the coil will be
1) 2A
2) 4A
3) 8A
a transformer is used to light a 100W and 110V lamp from a 220V mains. if the main current is 0.5A , then the efficiency of the transformer is approx.
1) 50%
2) 90%
2) 10%
4) 30%
in the AC circuit, the current is expressed as I= 100 sin 200pie t .in this circuit the current rises from zero to peak value in time
1) 1/400s
2) 1/300s
3) 1/100s
4) 1/200s
An ac - circuit having supply voltage E= 10sinwt consists of a resistor of resistance 3 ohm and an inductor of reactance 4 ohm connected in series. The voltage across the inductor at t =T /2 is
a. 2 V
b. b. 10V
c. 0 V
d. 4.8 V
ans in book is (d)
what is the approximate peak value of an alternating current producing 4 times the heat produced per second by a steady current of 2A in a resistor
1) 2.8A
3) 5.6A
4) 8A
an inductive circuit contains a resistance of 10ohm and an inductance of 2 henry . if an alternatic voltage of 120V and frequency 60Hz is applied to this circuit , the current in the circuit would be nearly
1) 0.30A
2) 0.80A
3) 0.48A
4) 0.16A
the time required for a 50Hz sinusoidal alternating current to change its value from zero to the rms value
1) 105*10-2s
2) 2.5*10-3s
3) 0.1s
4) 10-6s
if the power factor in an ac circuit changes from 1/3 to 1/9 then by what percent reactance will change(aproxx.) , if resistance remains constant?
1) increase by 200%
2) decrease by 200%
THE VIRTUAL CURRENT OF 4A anf 50Hz flows in an ac circuit containing a coil. the power consumed in the coils is 240W . if the virtual voltage across teh coil is 100V , then its resistance will be
1( 1/3pie
2)1/5pie
3) 15ohm
4) 1/pie ohm
an electric motor operates on a 50V supply and a current of 12A . if the efficiency of teh motor is 30% , what is the resisatnce of winding of motor?
1) 6ohm
2) 4ohm
3) 2.9ohm
4) 3.1ohm
a sinusoidal supply of frequency 10Hz and rms voltage 10V is connected to a 2.1*10-6 F capacitor . what is rms value of current?
1) 5.5mA
2) 20mA
3) 26mA
4) 1.6mA
The magnetic field energy of an inductor changes from max. value to min. value im 5 ms when connected to a a.c. source . What is the frequency of the source ?
if power factor is 1/2 in a series RL circuit . R=100ohm , then L is(s=50Hz)
1) pie H
2) (3)1/2/pie H
3) pie/(3)1/2 H
4) 2pie H
derive an expression for average power in AC circuit. .
simple and easy method
1. In L-C oscillation, maximum charge on the capacitor can be q. If at any instant electric energy and magnetic energy associated with circuit is equal, then charge on capacitor at that instant is:
a. Q/SQRT 2 B. Q/2 C. SQRT 3 Q/ 2 D. 3Q/2
a step down transformer is used on a 1000V line to deliver 20A at 120V at the secondary coil. if the efficeincy of the transformer is 80% the current drawn from the line is
1) 3A
2) 30A
3) 0.3A
4) 2.4A
what is the time required for a 50hz ac to change its value from 0 to rms value.??
reply fast plzzz....
sir , please make me clear when to use flemings right hand rule and left hand rule
a 110V dc heater is used on an ac source , such that the heat produced is same as it produces when connected to 100V dc in same time intervals. what would be the rms value of the alternating voltage
1) 110V
2) 220V
A part of circuit in a steady-state along with the currents flowing in the branches, the values of resistances, etc., is shown in the figure. Calculate the energy stored in the capacitor
a current of 5A is flowing at 220V in the primary of a transformer. if the voltage produced in the secondary coil is 2200V and 50% poer is lost , then the current in the secondawill be
1) 0.25A2) 0.5A3) 2.5A
4) 5A
1. An Ac source is rated as 222V, 60 HZ. The average voltage is calculated in a time interval of 16.67 ms, It
A. Must be zero
B. Maybe zero
C. Is never zero
D. Is (111 sqrt 2) V
how is large scale transmission of electrical energy over long distance with the use of transformer
What is power factor of a resonance series LCR circuit?
a series lcr circuit consisting of an inductor Land capacitor C and resistors R connected across a source of emf e= e'sin x(omega)t. when xL = 1/xC thecurrent in the circuit is I' and if angular frequency of source is changed to x', the current becomes I'/2, then the value |x,L - 1/x'C| is
1) R
2) (3)1/2 R
3) (15)1/2 R
4) zero
A resistance of 40 ohm is connected to an a.c. source of 220V, 50Hz. Find the time taken by the current to change from its maximum value to the rms value.
a coil of inductive reactance 31ohm has a resistance of 8ohm. it is placed with a condenser of capacitative reactance 25ohm. teh combination is connected to an ac source of 110V . the power factor is
1) 0.33
2) 0.56
3) 0.64
4) 0.80
In an ideal transformer,number of turns in the primary and secondary are 200 and 1000 respectively. If the power input to the primary is 10kW at 200V,calculate (a) output voltage and (b) current in the primary.
Explain core and shell type of transformer.
what is rms current of an AC?
A coil when connected across a 10V dc supply draws a current of 2A. When it is connected across a 10V-50 Hz ac supply, the same coil draws a current of 1A. Explain why it draws lesser current in the second case.Hence determine the self inductance of the coil. (Take = 3).
1--A current I=3+8sin100t is passing through a resistor of resistance 10ohm.the effective value of current is
Ans---5 A
obtain an expression for power of an LR ,CR and LCR circuit
How does quality factor change with resistance of the circuit?
What is the function of hot wire voltmeter ?
average energy loss due to inductance(L) of circuit is
1) i2rms
2) V2rms/XL
3) zero
E.g: 9876543210, 01112345678
We will give you a call shortly, Thank You
Office hours: 9:00 am to 9:00 pm IST (7 days a week)
Syllabus
equation of alternating current is given by I = 10(2)1/2sin(100piet + pie/6). the time taken by current to reach the root mean square value from t=0 is t1 then the value of t1 is
1) 1/1200s
2) 1/250s
3) 1/200s
4) 1/800s
in an oscillating L-C circuit , the maximum charge on the capacitor is Q. the charge on the capacitor , when the energy is stored equally between the electric and magnetic field is
1) Q/2
2) Q/(2)1/2
3) Q/(3)1/2
4) Q/3
a coil has resistance 30ohm and inductive reactance 20ohm at 50Hz frequency . if an AC source ,of 200V , 100Hz is connected across the coil, the current in the coil will be
1) 2A
2) 4A
3) 8A
a transformer is used to light a 100W and 110V lamp from a 220V mains. if the main current is 0.5A , then the efficiency of the transformer is approx.
1) 50%
2) 90%
2) 10%
4) 30%
in the AC circuit, the current is expressed as I= 100 sin 200pie t .in this circuit the current rises from zero to peak value in time
1) 1/400s
2) 1/300s
3) 1/100s
4) 1/200s
An ac - circuit having supply voltage E= 10sinwt consists of a resistor of resistance 3 ohm and an inductor of reactance 4 ohm connected in series. The voltage across the inductor at t =T /2 is
a. 2 V
b. b. 10V
c. 0 V
d. 4.8 V
ans in book is (d)
what is the approximate peak value of an alternating current producing 4 times the heat produced per second by a steady current of 2A in a resistor
1) 2.8A
2) 4A
3) 5.6A
4) 8A
an inductive circuit contains a resistance of 10ohm and an inductance of 2 henry . if an alternatic voltage of 120V and frequency 60Hz is applied to this circuit , the current in the circuit would be nearly
1) 0.30A
2) 0.80A
3) 0.48A
4) 0.16A
the time required for a 50Hz sinusoidal alternating current to change its value from zero to the rms value
1) 105*10-2s
2) 2.5*10-3s
3) 0.1s
4) 10-6s
if the power factor in an ac circuit changes from 1/3 to 1/9 then by what percent reactance will change(aproxx.) , if resistance remains constant?
1) increase by 200%
2) decrease by 200%
THE VIRTUAL CURRENT OF 4A anf 50Hz flows in an ac circuit containing a coil. the power consumed in the coils is 240W . if the virtual voltage across teh coil is 100V , then its resistance will be
1( 1/3pie
2)1/5pie
3) 15ohm
4) 1/pie ohm
an electric motor operates on a 50V supply and a current of 12A . if the efficiency of teh motor is 30% , what is the resisatnce of winding of motor?
1) 6ohm
2) 4ohm
3) 2.9ohm
4) 3.1ohm
a sinusoidal supply of frequency 10Hz and rms voltage 10V is connected to a 2.1*10-6 F capacitor . what is rms value of current?
1) 5.5mA
2) 20mA
3) 26mA
4) 1.6mA
The magnetic field energy of an inductor changes from max. value to min. value im 5 ms when connected to a a.c. source . What is the frequency of the source ?
if power factor is 1/2 in a series RL circuit . R=100ohm , then L is(s=50Hz)
1) pie H
2) (3)1/2/pie H
3) pie/(3)1/2 H
4) 2pie H
derive an expression for average power in AC circuit. .
simple and easy method
1. In L-C oscillation, maximum charge on the capacitor can be q. If at any instant electric energy and magnetic energy associated with circuit is equal, then charge on capacitor at that instant is:
a. Q/SQRT 2 B. Q/2 C. SQRT 3 Q/ 2 D. 3Q/2
a step down transformer is used on a 1000V line to deliver 20A at 120V at the secondary coil. if the efficeincy of the transformer is 80% the current drawn from the line is
1) 3A
2) 30A
3) 0.3A
4) 2.4A
what is the time required for a 50hz ac to change its value from 0 to rms value.??
reply fast plzzz....
(ii) When both X and Y are connected in series with R to the same source, will the power dissipated in circuit be maximum or min.? Justify
sir , please make me clear when to use flemings right hand rule and left hand rule
a 110V dc heater is used on an ac source , such that the heat produced is same as it produces when connected to 100V dc in same time intervals. what would be the rms value of the alternating voltage
1) 110V
2) 220V
A part of circuit in a steady-state along with the currents flowing in the branches, the values of resistances, etc., is shown in the figure. Calculate the energy stored in the capacitor
a current of 5A is flowing at 220V in the primary of a transformer. if the voltage produced in the secondary coil is 2200V and 50% poer is lost , then the current in the secondawill be
1) 0.25A2) 0.5A3) 2.5A
4) 5A
1. An Ac source is rated as 222V, 60 HZ. The average voltage is calculated in a time interval of 16.67 ms, It
A. Must be zero
B. Maybe zero
C. Is never zero
D. Is (111 sqrt 2) V
how is large scale transmission of electrical energy over long distance with the use of transformer
What is power factor of a resonance series LCR circuit?
a series lcr circuit consisting of an inductor Land capacitor C and resistors R connected across a source of emf e= e'sin x(omega)t. when xL = 1/xC thecurrent in the circuit is I' and if angular frequency of source is changed to x', the current becomes I'/2, then the value |x,L - 1/x'C| is
1) R
2) (3)1/2 R
3) (15)1/2 R
4) zero
A resistance of 40 ohm is connected to an a.c. source of 220V, 50Hz. Find the time taken by the current to change from its maximum value to the rms value.
a coil of inductive reactance 31ohm has a resistance of 8ohm. it is placed with a condenser of capacitative reactance 25ohm. teh combination is connected to an ac source of 110V . the power factor is
1) 0.33
2) 0.56
3) 0.64
4) 0.80
In an ideal transformer,number of turns in the primary and secondary are 200 and 1000 respectively. If the power input to the primary is 10kW at 200V,calculate (a) output voltage and (b) current in the primary.
Explain core and shell type of transformer.
Please give proper working .
Thank you .
what is rms current of an AC?
A coil when connected across a 10V dc supply draws a current of 2A. When it is connected across a 10V-50 Hz ac supply, the same coil draws a current of 1A. Explain why it draws lesser current in the second case.Hence determine the self inductance of the coil. (Take = 3).
1--A current I=3+8sin100t is passing through a resistor of resistance 10ohm.the effective value of current is
Ans---5 A
i=10 sin 300t A and v= 200 sin 300t volt.
what is the power dissipation in the circuit.
plz xplain the calculations.
obtain an expression for power of an LR ,CR and LCR circuit
How does quality factor change with resistance of the circuit?
What is the function of hot wire voltmeter ?
average energy loss due to inductance(L) of circuit is
1) i2rms
2) V2rms/XL
3) zero