**Description** : If resistance is 8 Ohm and current is 16 ampere then what will be the voltage and power?

**Answer** : 128 volts ,2048 watts

**Description** : A d.c. voltage of 230 V is imposed on an unloaded 230 V, 50 Hz transformer, it will
(A) give high secondary voltage (B) burn out
(C) give secondary voltage as per k (D) None of these

**Answer** : A d.c. voltage of 230 V is imposed on an unloaded 230 V, 50 Hz transformer, it will burn out

**Description** : A single phase 230 V/ 150 V , 1 kVA, 50 Hz transformer is supplied by 230 V AC supply. Find the full load primary and secondary current.

**Description** : A 20 ohm resistor and a 60 ohm resistor are connected in parallel to a voltage source. If the current in the 60 ohm resistor is one ampere, the current in the 20 ohm resistor will be: w) 1/3 ampere x) 2/3 ampere y) 1 ampere z) 3 amperes

**Answer** : ANSWER: Z -- 3 AMPERES

**Description** : what will be the capacitance if three capacitors connected in parallel each having value of 0.5 micro Farad ?

**Answer** : the total capacitace when connected in parallel Tc=total capacitor c1=c2=c3=0.5uf Tc=c1+c2+c3 Tc=1.5uf

**Description** : An LED is operated on a 12 volt automobile circuit. The voltage drop across the LED is 2 volts and the current must be limited to 50 milliamps to prevent its overheating and destruction. What size resistor must be used? w) 60 ohms x) 100 ohms y) 120 ohms z) 200 ohms

**Answer** : ANSWER: Z -- 200 OHMS

**Description** : lf slip of an induction machine is 0.02 and the stator supply frequency is 50 Hz, what will be the frequency of the rotor induced e.m.f.?
(A) 10 Hz (B) 50 Hz (C) 1 Hz (D) 2500 Hz

**Answer** : 1hz

**Description** :

The low voltage winding of a 400/230 V, 1-phase, 50 Hz transformer is to be connected to a 25 Hz, the supply voltage should be

**Answer** : The low voltage winding of a 400/230 V, 1-phase, 50 Hz transformer is to be connected to a 25 Hz, the supply voltage should be 115 V.

**Description** : If an incandescent lamp of 80 ohms resistance takes a current of 0.75 ampere, what voltage is required
to light it?
A.45 volts
B.60 volts
c.23 volts
D.None of these

**Answer** : V=IR = 80*0.75 = 60 volts

**Description** : A transformer at 25 Hz develops 20 W hysteresis loss and 50 W eddy current loss. If the applied voltage and frequency are doubled, the new core losses are
(A) 140 W (B) 180 W (C) 240 W (D) 480 W

**Answer** : A transformer at 25 Hz develops 20 W hysteresis loss and 50 W eddy current loss. If the applied voltage and frequency are doubled, the new core losses are 240 W

**Description** : The locked rotor current in a 3-phase, star connected 15 , kW 4 , pole 230 V , 50 Hz induction motor at rated conditions is 50 A. Neglecting losses and magnetizing current, the approximate locked rotor line current drawn when the motor is connected to a 236 , V 57 Hz supply is
(A) 58.5 A (B) 45.0 A (C) 42.7 A (D) 55.6 A

**Answer** : The locked rotor current in a 3-phase, star connected 15 , kW 4 , pole 230 V , 50 Hz induction motor at rated conditions is 50 A. Neglecting losses and magnetizing current, the approximate locked rotor line current drawn when the motor is connected to a 236 , V 57 Hz supply is 45.0 A

**Description** : A 3 phase, 400 volts, 50 Hz, 100 kW, 4 pole squirrel cage induction motor with a rated slip of 2% will have a rotor speed of: (A) 1500 rpm (B) 1470 rpm (C) 1530 rpm (D) 1570 rpm

**Answer** : 1470rpm

**Description** : The reactance offered by a capacitor to an alternating current of frequency 50 Hz is 10 ohm. If frequency is increased to 100 Hz, the reactance will be (a) 2.5 ohm (b) 5.0 ohm (c) 20.0 ohm (d) 40.0 ohm

**Answer** : Xc = 1/(2*pi*f*c) so when f is double .... Xc will be half ... Ans is 5ohm

**Description** :

What will be the value of the current (in Ampere) in a 40 cm long solenoid in a free space, if it has 400 turns, 2 cm of diameter and produces a magnetic field of 4mT at its center

**Description** : What would happen if a power transformer designed for operation on 50 Hz (frequency) were connected to a 500 Hz (frequency) source of the same voltage:
(A) Eddy Current and Hysteresis losses will be excessive
(B) Current will be too much high
(C) Transformer may start to smoke and burn
(D) No effect

**Answer** : What would happen if a power transformer designed for operation on 50 Hz (frequency) were connected to a 500 Hz (frequency) source of the same voltage: (A) Eddy Current and Hysteresis losses will be ... will be too much high (C) Transformer may start to smoke and burn (D) No effect

**Description** : For a 500 Hz frequency excitation, a 50 km long power line will be modeled as

**Answer** : For a 500 Hz frequency excitation, a 50 km long power line will be modeled as long line

**Description** :

The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance becomes_____ohms.

**Answer** : The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance becomes 10 ohms.

**Description** : Problem on resistance and resistivity 1

**Answer** : Problem on resistance and resistivity 1

**Description** : If 1 ampere current is flowing through a 100 mH coil, then energy stored in the coil is (a) 0.05 Joules (b) 0.5 Joules (c) 5.0 Joules (d) None of these

**Description** : Problem on temperature coefficient of resistance 1

**Answer** : Problem on temperature coefficient of resistance 1

**Description** : A single-phase, 230 V, 50 Hz ac mains fed step down transformer (4:1) is supplying power to a half-wave uncontrolled ac-dc converter used for charging a battery (12 V dc) with the series current limiting resistor being 19.04 Ohm. The charging current is
(A) 2.43 A (B) 1.65 A (C) 1.22 A (D) 1.0 A

**Answer** : A single-phase, 230 V, 50 Hz ac mains fed step down transformer (4:1) is supplying power to a half-wave uncontrolled ac-dc converter used for charging a battery (12 V dc) with the series current limiting resistor being 19.04 Ohm. The charging current is 1.0 A

**Description** : The frequency of direct current is _______ (1) Zero (2) 50 HZ (3) 60 HZ (4) 100 HZ

**Answer** : Zero

**Description** : The eddy current loss in an AC motor is 100 watts at 50 Hz. Its losses at 100 Hz will be: (A) 25 watts (B) 59 watts (C) 100 watts (D) 400 watts

**Answer** : The eddy current loss in an AC motor is 100 watts at 50 Hz. Its losses at 100 Hz will be: 400 watts

**Description** : Problem on resistance and resistivity 13

**Answer** : Problem on resistance and resistivity 13

**Description** : Problem on resistance and resistivity 12

**Answer** : Problem on resistance and resistivity 12

**Description** : Problem on resistance and resistivity 11

**Answer** : Problem on resistance and resistivity 11

**Description** : Problem on resistance and resistivity 10

**Answer** : Problem on resistance and resistivity 10

**Description** : Problem on resistance and resistivity 9

**Answer** : Problem on resistance and resistivity 9

**Description** : Problem on resistance and resistivity 8

**Answer** : Problem on resistance and resistivity 8

**Description** : Problem on resistance and resistivity 7

**Answer** : Problem on resistance and resistivity 7

**Description** : Problem on resistance and resistivity 6

**Answer** : Problem on resistance and resistivity 6

**Description** : Problem on resistance and resistivity 5

**Answer** : Problem on resistance and resistivity 5

**Description** : Problem on resistance and resistivity 4

**Answer** : Problem on resistance and resistivity 4

**Description** : Problem on resistance and resistivity 3

**Answer** : Problem on resistance and resistivity 3

**Description** : Problem on resistance and resistivity 2

**Answer** : Problem on resistance and resistivity 2

**Description** : In a 230 V, 50 Hz single-phase SCR bridge converter operating at a firing delay angle, α and with large R-L load, the input source current is
(A) sinusoidal current (B) constant dc current
(C) continuous rectangular pulses (D) alternating rectangular pulses

**Answer** : In a 230 V, 50 Hz single-phase SCR bridge converter operating at a firing delay angle, α and with large R-L load, the input source current is alternating rectangular pulses

**Description** :

**Problem on temperature coefficient of resistance 3**

**Answer** : Problem on temperature coefficient of resistance 3

**Description** : Problem on temperature coefficient of resistance 2

**Answer** : Problem on temperature coefficient of resistance 2

**Description** : A 230 V, 50 Hz phase controlled single-phase full-controlled SCR bridge converter draws 15 A constant dc current. If the source inductance is 3 mH, the drop in dc output voltage is
(A) 4.5 V (B) 6.75 V (C) 9 V (D) 13.5 V

**Answer** : A 230 V, 50 Hz phase controlled single-phase full-controlled SCR bridge converter draws 15 A constant dc current. If the source inductance is 3 mH, the drop in dc output voltage is 9 V

**Description** : If a capacitance is charged by a square wave current source, then the voltage across the capacitor will be (a) Square wave (b) Step function (c) Triangular wave (d) Zero

**Answer** : If a capacitor is charged by a square wave current source, the voltage across the capacitor is : triangular wave

**Description** : If the phase difference between two points is 120° for a wave with velocity of 360 m/ and frequency 500 Hz, then path difference between the two points is (1) 1 cm (2) 6 cm (3) 12 cm (4) 24 cm

**Answer** : 24 cm

**Description** :

If resistance is 20 Q. and inductance is 27 in a R-L series circuit, then time constant of this circuit will be?

**Answer** : 0.1s

**Description** : A lamp of 100W at 200V is supplied current at 100 volts. It will be equivalent to the lamp of:
a. 50W b. 40W c. 25W d. 10W

**Answer** : A lamp of 100W at 200V is supplied current at 100 volts. It will be equivalent to the lamp of: 25W

**Description** : If the supply frequency of a 3-phase induction motor is ‘f’, then frequency of rotor emf at motor slip ‘s’ will be
(a) sf (b) (1 – s)f (c) f/s (d) None of these

**Description** : The synchronous speed of an 8 pole induction motor supplied power from a 50 Hz source will be ?

**Answer** : Ns equals f/pair pole 50/4 - 12.5

**Description** :

For a frequency of 200 Hz, the time period will be?

**Answer** : For a frequency of 200 Hz, the time period will be 0.005 s.

**Description** : A 200 V, 50 Hz inductive circuit takes a current of 10 A at 30 degree lagging pf, what is the inductive reactance of the circuit?
(A) 17.8 Ω (B) 100 Ω (C) 178 Ω (D) 10 Ω

...