Current Electricity Test

Result

Current Electricity Test - 1

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Weekly Quiz Competition

Question 1
4 / -1

The electrical resistance of a conductor depends upon

A
size of conductor

B
temperature of conductor

C
geometry of conductor

D
all of these

Solution

The electrical resistance of a conductor is depend upon all factors i.e., size, temperature and geometry of conductor.
Question 2
4 / -1

The voltage V and current. I graphs for a conductor at two different temperatures T₁ and T₂ are shown in the figure.

The relation between T₁ and T₂ is

A
T₁ > T₂

B
T₁ < T₂

C
T₁ = T₂

D
T₁ = 1/T₂

Solution

The slope of V-I graph gives the resistance of a conductor at a given temperature.

From the graph, it follows that resistance of a conductor at temperature T₁ is greater than at temperature T₂. As the resistance of a conductor is more at higher temperature and less at lower temperature.
Hence T₁ >T₂.
Question 3
4 / -1

A wire of resistance 4Ω is used to wind a coil of radius 7cm. The wire has a diameter of 1.4mm and the specific resistance of its material is 2 × 10⁻⁷Ωm. The number of turns in the coil is

A
50

B
40

C
60

D
70

Solution

Let n be the number of turns in the coil. Then total length of wire used,
l = 2πr × n = 2π × 7 × 10⁻²× n
Total resistance, R =
or 4 =
∴ n = 70
Question 4
4 / -1

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

A
R

B
R/4

C
3R/4

D
R/2

Solution

The resistance of rod before reformation

Now the rod is reformed such that

∴ ( ∴ Volume remains constant)
or
Now the resistance of the rod after reformation

∴
or (using (i))
∴ R2 = R/4
Question 5
4 / -1

A wire with 15 Ω resistance is stretched by one tenth of its original length and volume of wire is kept constant. Then its resistance will be

A
15.18Ω

B
81.15Ω

C
51.18Ω

D
18.15Ω

Solution

If the wire is stretched by (1/10)^th of its original length then the new length of wire become

As the volume of wire remains constant then
⇒
Now the resistance of stretched wire.

=
∴
= 18.15Ω