Current Electricity Questions and Answers

5 a Find the Thevenin equivalent circuit of the circuit shown in Fig to the left of the terminals Then find the current through RL 6 16 and 3692 492 192 a 32 V 1292 12 V www Or b Using Thevenin s theorem find I 69 www 69Q www 2 A www 2 A 492 b b 19 RL

A 200 MVA synchronous generator having inertia constant 5MJ MVA is connected in parallel with a 150 MVA generators having inertia constant of 4 MJ MVA both the generator are swinging coherently the equivalent inertia constant of the machine on a base of 100 MVA is in MJ MVA

3 5 In the circuit shown in figure 3 376 E 5V r 19 R 40 R3302 and C 3uF Find the charge on the plates of capaictor A F ib HH C C R www R www R3 www Figure 376 HH C C

Assertion A Earthing provides a safety measure for electrical circuits and appliances Reason R When we bring a charged body in contact with the earth all the excess charge on the body disappears by causing a momentary current to pass to the ground through the connecting conductor A A

A cylindrical rod is reformed to half of its original length keeping volume constant If its resistance before this change were R then the resistance after reformation of rod will be R b R 4 RIA c 3R 4 d R 2

An certain resistor dissipates 0 5 W when connected to a 3 V potential difference When con nected to a 1 V potential difference this resistor will dissipate A 0 5 W B 0 167 W C 1 5 W D 0 056 W E none of these Test

To get maximum current through a resistance of 2 5 Q one can use m rows of cells each row having n cells The internal resistance of each cell is 0 5 Q What are the values of n m if the total number of cells is 45 3 15 5 9 X 9 5

In the arrangement shown in the figure initially the block of mass m is in limiting equilibrium The coefficient of friction between the block of mass m and floor is Now the particle of mass m is given a horizontal velocity v The initial distance of the block of mass m from the pulley is The masses of pulley and threads are negligible Choose the correct option s It m A Acceleration of m just after the velocity given is B Acceleration of m just after the velocity given is 1 u 1 20 C Radius of curvature of path of m just after the velocity given is 1 D Radius of curvature of path of m just after the velocity given is 2 1 u

10 kJ s of heat is produced when a DC flows through a 100 Q resistor Which of the following ac produces nearly same heat per sec through the same resistor 1 15 sin ot 3 30sin ot 2 45 sin wty 4 10 sin ot

kii 12 wires each of resistance r are connected in the form of 12 sides of a cube Effective resistance across a Diagonally opposite corners 5r 6 b Face diagonal 3r 4 c two adjacent corners 7r 12

A capacitor of capacity C is charged to a potential difference V and another capacitor of capacity 2 C is charged to a potential difference 2 V The charging batteries are disconnected and the two capacitors are connected to each other in parallel with reverse polarity The energy lost in this process will be 1 CV 2 3 C 2 2 CV

You buy a 75 W light bulb The label means that A no matter how you us B the bulb was filled with 75 W at the factory C the actual power dissipated will be much higher than 75 W since most of the power appe as heat D the bulb is expected to burn out after you use up its 75 W E none of the above

The cylinder is changed to one with the same mass and radius but a different moment of inertia Starting from rest the mass now moves a distance of 0 492 m in a time of 0 510 s Find Icm of the new cylinder

A point light source is located at a distance L from a screen A thir converging lens of focal length f L 4 and aperture radius R hel parallel to the screen makes a circular spot of light on the screen If len is moved from the source towards the screen size of the spot varies Fin the radius of the smallest light spot which can be obtained in this wa on the screen R FL 2VFL 2

10 In the Bohr model of hydrogen atom the electron rotates in a circle of radius 0 53 about the nucleus Calculate the energy in eV needed to tear the electron loose from the nucleus of the atom Ans 13 6 eV

If the current sensitivity of a moving coil galvanometer is increased by 20 its resistance also increases and becomes 1 5 times then the voltage sensitivity of galvanometer will Increase by 20 Increase by 50 Decrease by 25 Decrease by 20