Basic Electrical Engineering MCQs Part 6

Basic Electrical Engineering MCQs Part 6

Certain length of wire has a resistance of 6 ohms. What is the value of resistance of wire that is three times long and having two times the cross-sectional area

Certain length of wire has a resistance of 6 ohms. What is the value of resistance of wire that is three times long and having two times the cross-sectional area:

1. 1 ohm
2. 4 ohm
3. 9 ohm
4. 12 ohm

Correct answer: 3. 9 ohm

Solution:

R1 = ρ * l1 /a1

R2 = ρ * l2 /a2

R2 / R1 = (l2 / a2) * (a1 / l1)

R2 / R1 = (3l/2a) * (a/l) = 3/2 = 1.5

R2/R1 = 1.5

R2 = 1.5 * 6 = 9 ohms

A resistor having color coding Brown Black Red

A resistor having color coding:

Brown Black Red will have resistance:

1. 1 kΩ ± 10%
2. 1 kΩ ± 20%
3. 2 kΩ ± 10%
4. 2 kΩ ± 20%

Correct answer: 2. 1 kΩ ± 20%

Brown, Black = 10

Red = 10^2

None = ±20%

A solid cube of silver has mass 50 g. Considering density of silver 10.5 g/cm³ and resistivity to be 0.0000016 Ωcm. The resistance between two opposite faces of cube will be

A solid cube of silver has mass 50 g. Considering density of silver 10.5 g/cm³ and resistivity to be 0.0000016 Ωcm. The resistance between two opposite faces of cube will be:

1. 3.29 * 10^-7 Ω
2. 5.42 * 10^-7 Ω
3. 9.51 * 10^-7 Ω
4. None of these

Correct answer: 3. 9.51 * 10^-7 Ω

Solution:

Volume of cube = Mass/Density = 50/10.5 = 4.76 cm³

Each side of cube =4.76190476190476^1/3 = 1.68 cm

R = ρl/A = 9.51*10^-7 Ω

Temperature coefficient of resistance of Eureka is

Temperature coefficient of resistance of Eureka is:

1. Positive
2. Negative
3. Zero
4. None of these

Correct answer: 1. Positive

The mass of a proton is how many times the mass of electron

The mass of a proton is how many times the mass of electron.

1. 1 time (is equal to)
2. 3 times less than
3. 400 times
4. About 1837 times

Correct answer: 4. About 1837 times