CBSE Class 12 Physics Current Electricity Quiz 4

1. The temperature coefficient of resistance is expressed in :

A °C B °C^-1 C m°C^-1 D None of these

2. Copper wire is used as connecting wire because :

A copper has high electrical resistivity B copper has low electrical resistivity C copper has low electrical conductivity D copper has high value of elasticity

3. The heat sensitive device whose resistivity changes very rapidly with change of temperature is called a :

A resistor B super-conductor C thermocouple D thermistor

4. The phenomenon of super-conductivity was discovered by :

A Ohm B Onnes C Edison D None of these

5. The specific resistance of a conductor increases with :

A increase in temperature B increase in cross-sectional area C decrease in length D decrease in cross-sectional area

6. In an experiment with potentiometer, null point with a cell is found at 240 cm. When the cell is shunted with a resistance 2 Ω, the null point becomes 120 cm internal resistance of cell is :

A 4 Ω B 2 Ω C 1 Ω D \(\frac{1}{2}\) Ω

7. Two conductors of equal length and radii the ratio of 2 : 3 are; connected in parallel the source of electricity. The ratio of the velocity of electrons in the conductor be :

A 2 : 3 B 4 : 9 C 1 : 1 D 3 : 2

8. In questions 38, the maximum value of current (l_max) is given by the condition :

A l_max = α - \(\frac{β^2}{2γ}\) B l_max = α - \(\frac{β^2}{2α}\) C l_max = α - \(\frac{γ^2}{2β}\) D None of these

9. In questions 38, the line (t) after which the value of current reaches a maximum values given by :

A t = \(\frac{α}{β}\) B t = \(\frac{β}{α}\) C t = \(\frac{β}{γ}\ ) D t = \(\frac{γ}{β}\)

10. The smallest resistance that can be obtained by the combination of n resistors each resistance r is :

A \(\frac{r}{n}\) B nr C \(\frac{n}{r}\) D n²r