M.C.Q

MCQ 511 Mark

Which unit could be used to measure current?

A
Watt.
B
Coulomb.
C
Volt.
✓
Ampere.

Answer

Correct option: D.

Ampere.

It is the SI unit of electric current.

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MCQ 521 Mark

The resistance of a wire of length $300m$ and cross$-$section area $1.0\ mm^2$ made of material of resistivity $1.0\times10−7 \Omega \ \text{m}$ is:

A
$2 Ω$
B
$3 Ω$
C
$20 Ω$
✓
$30 Ω$

Answer

Correct option: D.

$30 Ω$

Resistance, $\text{R}=\frac{\rho\text{I}}{\text{A}}$
Length, $I = 300m$
Cross section area, $A = 1.0mm^2 = 10^{-6} m^2$
Resistivity, $\rho=1.0\times10^{-7}\Omega\ \text{m}$
Resistance, $\text{R}=\frac{10^{-7}\times300}{10^{-6}}$
$\text{R}=30\Omega$

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MCQ 531 Mark

How many joules of electrical energy are transferred per second by a 6V; 0.5A lamp?

✓
30J/ s
B
12J/ s
C
0.83J/ s
D
3J/ s

Answer

Correct option: A.

30J/ s

Electrical energy transferred per second, E = V × I × t = 6V × 0.5A × 1s 6V × 0.5A × 1s = 3J/ s

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MCQ 541 Mark

If the resistance of a certain copper wire is $1 Ω,$ then the resistance of a similar nichrome wire will be about:

A
$25 Ω$
B
$30 Ω$
✓
$60 Ω$
D
$45 Ω$

Answer

Correct option: C.

$60 Ω$

If the resistance of a certain copper wire is $1 Ω,$ the resistance of a similar nichrome wire will be about $60 Ω$ because the resistivity of nichrome is 60 times the resistivity of copper.

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MCQ 551 Mark

f the amount of electric charge passing through a conductor in 10 minutes is 300C, the current flowing is:

A
30A.
B
0.3A.
✓
0.5A.
D
5A.

Answer

Correct option: C.

0.5A.

Here, charge, Q = 300C
Time, t = 10 minutes = (10 × 60)s = 600s
Then, current, $\text{I}=\frac{\text{Q}}{\text{t}}$
$=\frac{300}{600}=0.5\text{A}.$

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MCQ 561 Mark

The heat produced in a wire of resistance $'x\ '$ when a current $'y\ '$ flows through it in time $'z\ '$ is given by:

A
$x^2 \times y \times z.$
✓
$x \times z \times y^2.$
C
$y \times z^2 \times x$.
D
$y \times z \times x.$

Answer

Correct option: B.

$x \times z \times y^2.$

This is so because heat, $H = I^2Rt.$

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Science M.C.Q