Ohm's law, resistance and V-I characteristics — practice questions

Question 1 · difficulty L2 · understanding

The variation of applied potential and current flowing through a given wire is shown in figure. The length of wire is 31.4 cm. The diameter of wire is measured as 2.4 cm. The resistivity of the given wire is measured as x $$\times$$ 10 $$-$$3 $$\Omega$$ cm. The value of x is ____________. [Take $$\pi$$ = 3.14]

Question 2 · difficulty L2 · understanding

The Colour coding on a carbon resistor is shown in the given figure. The resistance value of the given resistor is :

• A. (5700 $$\pm$$ 285) $$\Omega$$
• B. (7500 $$\pm$$ 750) $$\Omega$$
• C. (5700 $$\pm$$ 375) $$\Omega$$
• D. (7500 $$\pm$$ 375) $$\Omega$$

Question 3 · difficulty L2 · understanding

A conducting wire of length 'l', area of cross-section A and electric resistivity $$\rho$$ is connected between the terminals of a battery. A potential difference V is developed between its ends, causing an electric current. If the length of the wire of the same material is doubled and the area of cross-section is halved, the resultant current would be :

• A. $$4{{VA} \over {\rho l}}$$
• B. $${3 \over 4}{{VA} \over {\rho l}}$$
• C. $${1 \over 4}{{VA} \over {\rho l}}$$
• D. $${1 \over 4}{{\rho l} \over {VA}}$$

Question 4 · difficulty L3 · understanding

A uniform metallic wire carries a current 2 A, when 3.4 V battery is connected across it. The mass of uniform metallic wire is 8.92 $$\times$$ 10$$^{-3}$$ kg, density is 8.92 $$\times$$ 10$$^{3}$$ kg/m$$^3$$ and resistivity is 1.7 $$\times$$ 10$$^{-8}~\Omega$$-$$\mathrm{m}$$. The length of wire is :

• A. $$l=100$$ m
• B. $$l=6.8$$ m
• C. $$l=5$$ m
• D. $$l=10$$ m

Question 5 · difficulty L3 · understanding

In the experiment of Ohm's law, a potential difference of 5.0 V is applied across the end of a conductor of length 10.0 cm and diameter of 5.00 mm. The measured current in the conductor is 2.00 A. The maximum permissible percentage error in the resistivity of the conductor is :

• A. 3.9
• B. 8.4
• C. 7.5
• D. 3.0

Question 6 · difficulty L3 · understanding

Resistance of a carbon resistor determined from colour codes is $$(22000 \pm 5 \%) \Omega$$. The colour of third band must be :

• A. Green
• B. Orange
• C. Yellow
• D. Red

Question 7 · difficulty L3 · understanding

The color code of a resistance is given below : The values of resistance and tolerance, respectively, are

• A. 47 k$$\Omega$$ , 10%
• B. 4.7 k$$\Omega$$ , 5%
• C. 470 $$\Omega$$ , 5%
• D. 470 k$$\Omega$$ , 5%