JEE Questions for Physics Current Electricity I Quiz 16 - MCQExams.com

In the above questions, the resistance between the square faces is
  • 3 × 10–9Ω
  • 3 × 10–7Ω
  • 3 × 10–5Ω
  • 3 × 10–3Ω
There is a current of 1.344 amp in a copper wire whose area of cross-section normal to the length of the wire is 1 mm26 . If the number of free electrons per cm3 is 8.4 × 1022 , then the drift velocity would be
  • 1.0 mm/sec
  • 1.0 m/sec
  • 0.1 mm/sec
  • 0.01 mm/sec
The resistance of a wire at temperatures t° C and 0° C are related by

  • Physics-Current Electricity I-65681.png
  • 2)
    Physics-Current Electricity I-65682.png

  • Physics-Current Electricity I-65683.png

  • Physics-Current Electricity I-65684.png
A voltmeter has a range 0–V with a series resistance R. With a series resistance 2R, the range is 0–V\'. Thecorrect relation between V and V\' is
  • V' = 2V
  • V' > 2V
  • V' >> 2V
  • V' < 2V
A certain piece of silver of given mass is to be made like a wire. Which of the following combinations of length(L) and the area of cross-section (A) will lead to the smallest resistance?
  • L and A
  • 2L and A/2
  • L/2 and 2A
  • Any of the above, because volume of silver remains same
The resistance of a wire is 10 Ω. Its length is increased by 10% by stretching. The new resistance will now be
  • 12 Ω
  • 1.2 Ω
  • 13 Ω
  • 11 Ω
Resistance of tungsten wire at 150°C is 133 Ω. Its resistance temperature coefficient is 0.0045/°C. Theresistance of this wire at 500°C will be
  • 180 Ω
  • 225 Ω
  • 258 Ω
  • 317 Ω
A metal wire of specific resistance 64 × 10–6 ohm–cmand length 198 cm has a resistance of 7 ohm, the radius of the wire will be
  • 2.4 cm
  • 0.24 cm
  • 0.024 cm
  • 24 cm
The resistance of a wire is R. If the length of the wire is doubled by stretching, then the new resistance will be
  • 2R
  • 4R
  • R
  • R/4
A potential difference of V is applied at the ends of a copper wire of length 1 and diameter d. On doubling only d, drift velocity
  • Becomes two times
  • Becomes half
  • Does not change
  • Becomes one fourth
Two resistances of 10 Ω and 20 Ω and an inductor of inductance 5 H are connected to a battery of 2V through a key k as shown in the figure. At time t = 0, when the key k is dosed the initial current through thebattery is
Physics-Current Electricity I-65701.png
  • 0.2A
  • 2)
    Physics-Current Electricity I-65702.png

  • Physics-Current Electricity I-65703.png
  • 0
In a wire of circular cross–section with radius r, free electrons travel with a drift velocity V when a current I flows through the wire. What is the current in another wire of half the radius and of the same material when the drift velocity is 2V?
  • 2I
  • I
  • I/2
  • 1/4
In a neon discharge tube 2.9 × 1018 Ne+ ions move to the right each second while 1.2 × 1018, electrons move to the left per second. Electron charge is 1.6 × 10–19 C. The current in the discharge tube
  • 1 A towards right
  • 0.66 A towards right
  • 0.66 A towards left
  • Zero
A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/quantities constant along the length of the conductor is/are
  • Current, electric field and drift speed
  • Drift speed only
  • Current and drift speed
  • Current only
The resistivity of alloys = Ralloy; the resistivity of constituent metals Rmetal. Then, usually
  • Ralloy = Rmetal
  • Ralloymetal
  • There is no simple relation between Ralloy and Rmetal
  • Ralloy> Rmetal
The resistance of a wire at room temperature 30° C is found to be 10 Ω. Now to increase the resistance by 10%, the temperature of the wire must be [The temperature coefficient of resistance of the material of the wire is 0.002 per °C]
  • 36°C
  • 83°C
  • 63°C
  • 33° C
The colour code for a resistor of resistance 3.5k Ω with5% tolerance is
  • Orange, green, red and gold
  • Red, yellow, black and gold
  • Orange, green, orange and silver
  • Orange, green, red and silver
Masses of three wires of copper are in the ratio of 1 : 3 : 5 and their lengths are in the ratio of 5 : 3 : 1. The ratio of their electrical resistances are
  • 1 : 3 : 5
  • 5 : 3 : 1
  • 1 : 15 : 125
  • 125 : 15 : 1
Conductivity increases in the order of
  • Al, Ag, Cu
  • Al, Cu, Ag
  • Cu, Al, Ag
  • Ag, Cu, Al
A uniform wire of resistance R is uniformly compressed along its length, until its radius becomes n times the original radius. Now resistance of the wire becomes

  • Physics-Current Electricity I-65717.png
  • 2)
    Physics-Current Electricity I-65718.png

  • Physics-Current Electricity I-65719.png

  • Physics-Current Electricity I-65720.png
The resistance of a conductor is 5 ohm at 50°C and6 ohm at 100°C. Its resistance at 0°C is
  • 1 ohm
  • 2 ohm
  • 3 ohm
  • 4 ohm
Equal potentials are applied on an iron and copper wire of same length. In order to have the same current flow in the two wires, the ratio r (iron)/r (copper) of their radii must be (Given that specific resistance of iron = 1.0 × 10–7ohm–m and specific resistance of copper= 1.7 × 10–8 ohm-m)
  • About 1.2
  • About 2.4
  • About 3.6
  • About 4.8
An electron (charge = 1.6 × 10–19 coulomb) is moving in a circle of radius 5.1 × 10–11m at a frequency of 6.8 × 1012 revolutions/sec. The equivalent current isapproximately
  • 5.1 × 10–13 amp
  • 6.8 ×10–3 amp
  • 1.1 × 10–3 amp
  • 2.2 ×10–3 amp
At what temperature will the resistance of a copper wire become three times its value at 0°C (Temperature coefficient of resistance for copper = 4 ×10–3 per ° C )?
  • 400°C
  • 450°C
  • 500°C
  • 550°C
If potential v = 100 ± 0.5 Volt and current I = 10 ± 0.2 amp are given to us, then what will be the value of resistance?
  • 10 ± 0.7 ohm
  • 5 ± 2 ohm
  • 0.1 ± 0.2ohm
  • None of these
A nichrome wire 50 cm long and one square millimetre cross-section carries a current of 4A when connected to a 2V battery. The resistivity of nichrome wire in ohm metre is
  • 1× 10–6
  • 4 × 10–7
  • 3 × 10–7
  • 2 × 10–7

Physics-Current Electricity I-65729.png

  • Physics-Current Electricity I-65730.png
  • 2)
    Physics-Current Electricity I-65731.png

  • Physics-Current Electricity I-65732.png

  • Physics-Current Electricity I-65733.png
At room temperature, copper has free electron density of 8.4 × 1028 per m3. The copper conductor has across-section of 10–6 m2 and carries a current of 5.4 A.The electron drift velocity in copper is
  • 400 m/s
  • 0.4 m/s
  • 0.4 m/s
  • 72 m/s
The resistance of a 5 cm long wire is 10 Ω. It is uniformly stretched so that its length becomes 20 cm. The resistance of the wire is
  • 160 Ω
  • 80 Ω
  • 40 Ω
  • 20 Ω
In the figure a carbon resistor has bands of different colours on its body as mentioned in the figure. The value of the resistance is
Physics-Current Electricity I-65737.png
  • 2.2 k Ω
  • 3.3 k Ω
  • 5.6 k Ω
  • 9.1 k Ω
Which of the following is vector quantity?
  • Current density
  • Current
  • Wattless current
  • Power
A current of 1 mA is flowing through a copper wire. How many electrons will pass a given point in one second [ e = 1.6 × 10–19Coulomb] ?
  • 6.25 × 1019
  • 6.25 × 1015
  • 6.25 × 1031
  • 6.25 × 108
The drift velocity of free electrons in a conductor is ‘v’ when a current i is flowing in it. If both the radius and current are doubled, then drift velocity will be
  • v
  • v/2
  • v/4
  • v/8
If σ1, σ2 and σ3 are the conductance’s of three conductors, then their equivalent conductance, whenthey are joined in series, will be

  • Physics-Current Electricity I-65741.png
  • 2)
    Physics-Current Electricity I-65742.png

  • Physics-Current Electricity I-65743.png
  • None of these
The resistance of a conductor increases with
  • Increase in length
  • Increase in temperature
  • Decrease in cross-sectional area
  • All of the above
Two wires that are made up of two different materials whose specific resistance are in the ratio 2 : 3, length 3 : 4 and area 4 : 5. The ratio of their resistances is
  • 6 : 5
  • 6 : 8
  • 5 : 8
  • 1 : 2
When a current flows through a conductor its temperature
  • May increase or decrease
  • Remains same
  • Decreases
  • Increases
What length of the wire of specific resistance 48 × 10–8Ωm is needed to make a resistance of 4.2 Ω? (diameter of wire = 0.4 mm)
  • 4.1 m
  • 3.1 m
  • 2.1 m
  • 1.1 m
We have two wires A and B of same mass and same material. The diameter of the wire A is half of that B. If the resistance of wire A is 24 ohm then the resistance ofwire B will be
  • 12 Ohm
  • 3.0 Ohm
  • 1.5 Ohm
  • None of these
The graph between resistivity and temperature, for a limited range of temperatures, is a straight line for a material like
  • Copper
  • Nichrome
  • Silicon
  • Mercury
  • Gallium arsenide
The length of the wire is doubled. Its conductance willbe
  • Unchanged
  • Halved
  • Quadrupled
  • 1/4 of the original value
A source of e.m.f. E = 15 V and having negligible internal resistance is connected to a variable resistance so that the current in the circuit increases with time as i = 1.2 t + 3. Then, the total charge that will flow in first five seconds will be
  • 10 C
  • 20 C
  • 30 C
  • 40 C
A thick wire is stretched so that its length becomes two times. Assuming that there is no change in its density, what is the ratio of change in resistance of wire to the initial resistance of wire?
  • 2 : 1
  • 4 : 1
  • 3 : 1
  • 1 : 4
The alloys constantan and manganin are used to make standard resistance because they have
  • Low resistivity
  • High resistivity
  • Low temperature coefficient of resistance
  • Both (b) and (c)
The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then
  • The resistance will be doubled and the specific resistance will be halved
  • The resistance will be halved and the specific resistance will remain unchanged
  • The resistance will be halved and the specific resistance will be doubled
  • The resistance and the specific resistance, will both remain unchanged
A wire of diameter 0.02 metre contains 1028 free electrons per cubic metre. For an electrical current of 100 A, the drift velocity of the free electrons in the wire is nearly
  • 1 × 10–19 m/s
  • 5 × 10–10 m/s
  • 2 × 10–4 m/s
  • 8 × 103 m/s
The colour sequence in a carbon resistor is red, brown, orange and silver. The resistance of the resistor is
  • 21 × 103 ± 10%
  • 23 × 101 ± 10%
  • 21 × 103 ± 5%
  • 12 × 103 ± 5%
A colour coded carbon resistor has the colours orange, blue, green and silver. Its resistance value and tolerancepercentage respectively are
  • 36 × 105Ω and 10%
  • 36 × 104Ω and 5%
  • 63 × 105Ω and 10%
  • 36 × 106Ω and 5%
The tolerance level of a resistor with the colour code red, blue, orange, gold is
  • ± 5%
  • ± 10%
  • ± 20%
  • ± 40%
Two identical conductors maintained at same temperatures are given potential differences in the ratio 1 : 2. Then the ratio of their drift velocities is
  • 1 : 2
  • 3 : 2
  • 1 : 1
  • 1 : 21/2
0:0:1


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