EASY
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A copper rod of cross-sectional area A carries a uniform current I through it. At temperature T, if the volume charge density of the rod is ρ, how long will the charges take to travel a distance d?

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Important Questions on Electricity

EASY
Across a metallic conductor of non-uniform cross section a constant potential difference is applied. The quantity which remains constant along the conductor is:
EASY
A resistor develops 800 J of thermal energy in 20 s when a current of 4 A is passed through it. If the current is increased from 4 A to 8 A, what will be the  energy developed in 20 s ?
EASY

Consider an electrical conductor connected across a potential difference V. Let Δq be a small charge moving through it in time Δt. If I is the electric current through it,
(i) the kinetic energy of the charge increases by IVΔt
(ii) the electric potential energy of the charge decreases by IVΔt.
(iii) the thermal energy of the conductor increases by IVΔt.

Then the correct statements is/are

EASY

The unit of current element is         
 

EASY
Estimate the magnitude of current that passes through a wire, if 0.1 mol of electrons flow through it in 40 min. (Assume Avogadro number =6×1023)
MEDIUM

The current flowing through a wire depends on time as I=3t2+2t+5. The charge flowing through the cross section of the wire in time from t=0 to t=2 s is

EASY
Solar energy of 200 Wm-2 is incident on a horizontal surface. If 20% of this energy can be converted into useful electrical energy, the area needed to supply 8 kW energy is
MEDIUM
The charge flowing in a conductor changes with time as Qt=αt-βt2+γt3, where α, β and γ are constants. Minimum value of current is:
EASY

A conducting wire of length l, area of cross-section A and electric resistivity ρ is connected between the terminals of a battery. A potential difference V is developed between its ends, causing an electric current. If the length of the wire of the same material is doubled and the area of cross-section is halved, the resultant current would be___

EASY

A heating coil of resistance 100 Ω takes 100 s to boil certain amount of water. If a similar heating coil is connected in series with the heating coil, then the time required to boil the water is ts, while tp time is required to boil the same amount of water if the coils are connected in parallel. What will be tstp?

EASY
The resistance of an ideal ammeter should be:
HARD

Shown in the figure is a semicircular metallic strip that has thickness t and resistivity ρ. Its inner radius is R1 and outer radius is R2. If a voltage V0 is applied between its two ends, a current I flows in it. In addition, it is observed that a transverse voltage ΔV develops between its inner and outer surfaces due to purely kinetic effects of moving electrons (ignore any role of the magnetic field due to the current). Then (figure is schematic and not drawn to scale)

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MEDIUM
In a hydrogen atom, the electron is moving in a circular orbit of the radius 5×10-11m with a constant speed of 2×106m/s. The electric current formed due to the motion of electron is________.(e=1.6×10-19C)
MEDIUM

Three resistors having resistances r1, r2 and r3 are connected as shown in the given circuit. The ratio i3i1 of currents in terms of resistances used in the circuit is :

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EASY

In an atom electron revolve around the nucleus along a path of radius 0.72 A making 9.4×1018 revolutions per second. The equivalent current is [Given e=1.6×10-19C]

EASY
A conductor carries a current of 300 mA. The number of electrons passing through it in 1 minute are ___ .
EASY

In a coil of resistance 100 Ω, a current is induced by changing the magnetic flux through it as shown in the figure. The magnitude of change in flux through the coil is:
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MEDIUM

An electric cable having a resistance R delivers 11 kW of power at 220 V to a factory. If the efficiency of transmission is 91%, then what is the value of R?

EASY

The potential difference between points A and B of adjoining figure is

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EASY
Which of the following acts as a circuit protective device?