Quiz 1 electric current

Two wires a and b , each of length 40 m and area of cross section 10^-2 m

, are

joined in series and potential difference of 60 Volt is applied between the ends of

combined wire. Their resistances are respectively 40 and 20 ohm.

Determine the ratio between their specific resistance.

• 2 : 1

• 1 : 2

• 1 : 1

cylindrical wire is stretched to increase its length by 10%. Calculate the

percentage increase in the resistance of this wire.

• 21%

• 10%

• 121 %

The table below lists various characteristics of two metallic wires, A and B.

If wire A has a resistance of R, then wire B has a resistance of..

• R

• 2R

• 4 R

The four wires shown below are made from the same resistive material. Rank the resistance in the wires

from low to high. Explain your answer.

• D, C, A, B

• A, B, D, C

• C, D, A, B

The four wires shown below are made from the same resistive material. The ratio between resistance of (D) to its of (B) is...

• 1 : 8

• 1 : 4

• 1 : 2

• 4 : 1

V in = 12V

Z1 = 3Ω

In the circuit above, your aim is to limit the current to 1A

, so you must design a resistor to serve in the place of Z2 .

To make this resistor, you have a spool of mystery metal, which has a cross sectional area of 1mm^2

and a resistivity of, ρ=3*10^-3 Ω.m

. What length of wire should you cut

• 3 mm

• 1mm

• 150 mm

You have a very long wire connected to an electric station. Even though you are suppling 120V from the source, by the time it reaches the station, there is a loss of voltage. The wire is 100 meters long.

If 100V

reaches the power station, what is the resistance per unit length of the wire? Assume a current of 2A.

• 0.1 Ω/m

• 10 Ω/m

• 0.5 Ω/m

Which of the following actions would increase the resistance of a wire by a factor of 4 ?

• Reduce the diameter of the wire to the half

• Increase the length of the wire to double

• Halving the cross-sectional area of the wire

Find the resistivity of a cylindrical wire with resistance 100Ω

, length 2m

, and cross sectional area of 4mm^2

• 0.2 mΩ. m

• 0.2 nΩ. m

• 2 mΩ. m

If a current intensity passing through a wire increases to the double , so that it's resistance.

• Decreases to half

• Increases to double

• Remains the same