Paper Questions (Raw)
Q1. The graph shows variation of current against applied potential difference, of a wire. The resistance of the wire is
1) (3.3 k "," ")
2) (6.6 k "," ")
3) (1.5 k "," ")
4) (9 k "," ")
Hint: $$R=\frac{dV}{dI}=\frac{15-5}{(6-3) \times 10^{-3}}=\frac{10}{3} \times 10^{3} \Omega=3.3 k \Omega$$
Q2. In which region of V-I graph of a specimen, is the resistance negative?
1) OA
2) AB
3) BC
4) Both AB and BC
Hint: $$Slope = R = \frac{V}{I}$$
At any point between A and B , tangent drawn has negative slope. Hence resistance will be negative. 
Q3. A metal rod is connected to a source of E.M.F. If it is compressed, so that its area of cross-section, increases by (0.1 %), the current in it will
Hint: $$i=\frac{V}{R} \Rightarrow i \propto \frac{1}{R}$$
On stretching or compressing, volume is conserved.
$$\therefore R \propto \frac{1}{A^{2}} \Rightarrow i \propto A^{2}$$
As
(A \uparrow es by 0.1 %),
(i \uparrow es by (2 \times 0.1 %) = 0.2 %)
Q4. A wire, having a resistance of (6 \Omega) per unit area per unit length and length of 3 m , is connected to a source of potential difference of 18 V . The current through the wire, if area of cross-section is (6 cm^{2}), is
1) 0.3 mA
2) 1.2 mA
3) 0.5 mA
4) 0.6 mA
Hint: ("," = Resistance per unit area per unit length) $$=6 \Omega-m$$
$$V=iR=i(\frac{\rho L}{A})$$
$$=\frac{VA}{\rho L}=\frac{18 \times 6 \times 10^{-4}}{6 \times 3}=0.6 mA$$
Q5. When a potential difference of V is applied across the ends of a conductor of length L , diameter of cross section (D), and resistivity (","), the current through it is (I). The potential difference per unit length of the conductor is
1) (\frac{4 I \rho}{\pi D^{2}})
2) (\frac{I \rho}{\pi D^{2}})
3) (\frac{\pi D^{2}}{4 I \rho})
4) (\frac{\pi D^{2}}{I \rho})
Hint: $$V=iR=i(\frac{\rho L}{\pi D^{2} / 4})$$
$$\frac{V}{L}=\frac{4 I \rho}{\pi D^{2}}$$
Q6. In an experiment, to study Ohm's law, a potential difference of 5 V is connected across a (10 \Omega) resistance. An ammeter is connected in series with the E.M.F. source to measure the current and a voltmeter is connected across the resistance to measure the potential difference. The ammeter and the voltmeter readings can be i i = 5
1) (0.5 A, 5 V)
2) (0.52 A, 5.2 V)
3) (0.48 A, 4.5 V)
4) (0.5 A, 1 V)
Hint: Ammeter has its own resistance. "," Total resistance in circuit increases
Q7. Select the CORRECT statement.
1) Both linear and non-linear resistances obey Ohm's law.
2) Non-linear resistance obeys Ohm's law but not the linear resistance.
3) Both linear and non-linear resistances do not obey Ohm's law.
4) Only linear resistance obeys Ohm's law.
Hint: Graph of Ohm's law is a straight line, characteristics of linear resistance is same.
Q8. A graph of potential difference between two points on a current carrying conductor and the distance between them is
1) parabola.
2) curve.
3) straight line.
4) circle.