HARD

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A conductor is made of an isotropic material (resistivity $ρ$ ) has rectangular cross-section. Horizontal dimension of the rectangle decreases linearly from $2 x$ at one end to $x$ at the other end and vertical dimension increases from $y$ to $2 y$ as shown in figure. Length of the conductor along the axis is equal to $l$ . A battery is connected across this conductor. Then:

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Important Questions on Current Electricity

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

A resistor dissipates $192 J$ of energy in $1 s$ when a current of $4 A$ is passed through it. Now, when the current is doubled, the amount of thermal energy dissipated in $5 s$ is _____________ $J .$

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

The charge flowing through a resistance

R

varies with time

t

Q = a t - b t^{2}

where

a

and

b

are positive constants. The total heat produced in

R

is:

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

An electric bulb is rated

220 V

and

100 W

. What is the power consumed by it when operated on

110 V ?

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

Question Image

The heat developed across $6 Ω$ resistor second is $50 J$ . Calculate the heat developed per second across $2 Ω$ resistor in the given electric circuit.

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

$A D C$ source with internal resistance $R_{0}$ is connected to circuit as shown in the figure. The value of $R$ for which the power generated in the circuit is the maximum is

Question Image

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

Two resistors $R_{1}$ and $R_{2}$ of $4 Ω$ and $6 Ω$ are connected in parallel across a battery. The ratio of power dissipated in them, P1 : P2 will be

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

A small town is located

10 km

away from a power plant. An average of

120 kW

of electric power is sent to this town. The transmission lines have a total resistance of

0.40 Ω .

Calculate the power loss, if the power is transmitted at

240 V .

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

A cell of internal resistance

r

passes current for some time in a resistor

R_{1}

, in another resistance

R_{2}

current is passed for the same time. If same heat is produced in the two resistors them show that

r = \sqrt{R_{1} R_{2}}

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

A resistor develops

500 J

of thermal energy in

20 s

when a current of

1.5 A

is passed through it. If the current is increased from

1.5 A

3 A

, what will be the energy developed in

20 s

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

The energy dissipated by a resistor is

10 mJ

1 s

, when an electric current of

2 mA

flows through it. The resistance is ________

Ω

. (Round off to the Nearest Integer)

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

An electric bulb is rated as $250 V, 750 W$ . Calculate the resistance of its filament.

HARD

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

The resistance of an electrical toaster has a temperature dependence given by

R (T) = R_{0} [1 + α (T - T_{0})]

in its range of operation. At

T_{0} = 300 K, R = 100 Ω and a t T = 500 K, R = 120 Ω

. The toaster is connected to a voltage source at

200 V

and its temperature is raised at a constant rate from

300 to 500 K

30 s

. The total work done in raising the temperature is :

Note: This question was awarded as the bonus since all options were incorrect in the exam.

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

An electric bulb is marked 200 V, 100 W. Calculate electrical resistance of its filament. If five such bulbs are connected in series to a 200 V supply, how much current will flow through them ?

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

Write the mathematical expression for Joule's law of heating.

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

A heater coil is cut into two equal parts and only one part is used for heating. The heat generated will now be

HARD

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

A voltage source whose open circuit voltage is

V_{0}

has an internal resistance

r

. The maximum power it can deliver to an external load connected across its output terminals is

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

Obtain Joules' law for Joule heating and state the law.

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

The resistor

R_{1} = 3 Ω

and

R_{2} = 1 Ω

are connected in parallel to a

20 V

battery. Find the heat developed in the resistor

R_{1}

in one minute

HARD

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

Heater of an electric kettle is made of a wire of length

L

and diameter

d

. It takes

4

minutes to raise the temperature of

0.5 kg

water by

40 K

. This heater is replaced by a new heater having two wires of the same material, each of length

L

and diameter

2 d

. The way these wires are connected is given in the options. How much time in minutes will it take to raise the temperature of the same amount of water by

40 K

HARD

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

In the circuit shown, the resistance r is a variable resistance. If for

r = f R

, the heat generation in r is maximum then the value of

f

Important Questions on Current Electricity

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