Page 1 [1] Test - 02 (Electrostatics & Current Electricity) 1. Coulomb’s law is true for : (a) atomic distances (= 10 -11 m) (b) nuclear distances (= 10 -15 m) (c) charged as well as uncharged particles (d) all the distances but for point object 2. Two conducting spheres of radii r 1 and r 2 are equal charged. The ratio of their charges is : (a) r 1 /r 2 (b) r 2 /r 1 (c) 2 2 2 1 r / r (d) 2 1 2 2 r / r 3. Three identical point charges, as shown are placed at the vertices of an isosceles right angles triangle. Which of the numbered vectors coincides in direction with the electric field at the mid-point M of the hypotenuse : (a) 1 (b) 2 (c) 3 (d) 4 4. The figure gives the electric potential V as a function of distance through five regions on x-axis. Which of the following is true for the electric field E in these regions : (a) E 1 > E 2 > E 3 > E 4 > E 5 (b) E 1 = E 3 = E 5 and E 2 < E 4 (c) E 2 = E 4 = E 5 and E 1 < E 3 (d) E 1 < E 2 < E 3 < E 4 < E 5 5. The capacity of a parallel plate air capacitor is 10 µF and it is given a charge 40 µC. The electrical energy stored in the capacitor in ergs is : (a) 80 × 10 6 (b) 800 (c) 8000 (d) 20000 6. Separation between the plates of a parallel plate capacitor is d and the area of each plate is A. When a slab of material of dielectric constant k and thickness t (t < d) introduced between the plates, its capacitance becomes : (a) ? ? ? ? ? ? - + e k 1 1 t d A 0 (b) ? ? ? ? ? ? + + e k 1 1 t d A 0 (c) ? ? ? ? ? ? - - e k 1 1 t d A 0 (d) ? ? ? ? ? ? + - e k 1 1 t d A 0 7. Can a condenser be given any amount of charge : (a) Yes (b) No (c) Depends on its shape (d) Depends on dielectric 8. In the figure bellows, what is the potential difference between the point A and B and between B and C respectively in steady state (a) V AB = 100volts. V BC = 100 volts (b) V AB = 75volts. V BC = 25 volts (c) V AB = 25volts. V BC = 75 volts (d) V AB = 50volts. V BC = 50 volts 9. A light bulb, a capacitors and a battery are connected together as shown here, with switch s initially open. When the switch S is closed, which one of the following is true ? (a) the bulb will light up for an instant when the capacitors starts charging (b) the bulb will light up when the capacitor is fully charged (c) the bulb will not light up at all (d) the bulb will light up and go off at regular internals 10. What air is replaced by dielectric medium of constant k, the maximum force of attraction between two charges separated by a distance (a) Decreases k times (b) Remains unchanged (c) Inreases k times (d) Increases k –1 time 11. The electric potential V is given as a function of distance × (metre) by V = (5x 2 + 10x – 9) volt. Value of electric field at x = 1m is (a) 20 V/m (b) 6 V/m (c) 11 V/m (d) –23 V/m 12. If E a be the electric field strength of a short dipole at a point on its axial line and E e that on the equatorial line at the same distance, then (a) E e = 2E a (b) E a = 2E e (c) E a = E e (d) none Page 2 [1] Test - 02 (Electrostatics & Current Electricity) 1. Coulomb’s law is true for : (a) atomic distances (= 10 -11 m) (b) nuclear distances (= 10 -15 m) (c) charged as well as uncharged particles (d) all the distances but for point object 2. Two conducting spheres of radii r 1 and r 2 are equal charged. The ratio of their charges is : (a) r 1 /r 2 (b) r 2 /r 1 (c) 2 2 2 1 r / r (d) 2 1 2 2 r / r 3. Three identical point charges, as shown are placed at the vertices of an isosceles right angles triangle. Which of the numbered vectors coincides in direction with the electric field at the mid-point M of the hypotenuse : (a) 1 (b) 2 (c) 3 (d) 4 4. The figure gives the electric potential V as a function of distance through five regions on x-axis. Which of the following is true for the electric field E in these regions : (a) E 1 > E 2 > E 3 > E 4 > E 5 (b) E 1 = E 3 = E 5 and E 2 < E 4 (c) E 2 = E 4 = E 5 and E 1 < E 3 (d) E 1 < E 2 < E 3 < E 4 < E 5 5. The capacity of a parallel plate air capacitor is 10 µF and it is given a charge 40 µC. The electrical energy stored in the capacitor in ergs is : (a) 80 × 10 6 (b) 800 (c) 8000 (d) 20000 6. Separation between the plates of a parallel plate capacitor is d and the area of each plate is A. When a slab of material of dielectric constant k and thickness t (t < d) introduced between the plates, its capacitance becomes : (a) ? ? ? ? ? ? - + e k 1 1 t d A 0 (b) ? ? ? ? ? ? + + e k 1 1 t d A 0 (c) ? ? ? ? ? ? - - e k 1 1 t d A 0 (d) ? ? ? ? ? ? + - e k 1 1 t d A 0 7. Can a condenser be given any amount of charge : (a) Yes (b) No (c) Depends on its shape (d) Depends on dielectric 8. In the figure bellows, what is the potential difference between the point A and B and between B and C respectively in steady state (a) V AB = 100volts. V BC = 100 volts (b) V AB = 75volts. V BC = 25 volts (c) V AB = 25volts. V BC = 75 volts (d) V AB = 50volts. V BC = 50 volts 9. A light bulb, a capacitors and a battery are connected together as shown here, with switch s initially open. When the switch S is closed, which one of the following is true ? (a) the bulb will light up for an instant when the capacitors starts charging (b) the bulb will light up when the capacitor is fully charged (c) the bulb will not light up at all (d) the bulb will light up and go off at regular internals 10. What air is replaced by dielectric medium of constant k, the maximum force of attraction between two charges separated by a distance (a) Decreases k times (b) Remains unchanged (c) Inreases k times (d) Increases k –1 time 11. The electric potential V is given as a function of distance × (metre) by V = (5x 2 + 10x – 9) volt. Value of electric field at x = 1m is (a) 20 V/m (b) 6 V/m (c) 11 V/m (d) –23 V/m 12. If E a be the electric field strength of a short dipole at a point on its axial line and E e that on the equatorial line at the same distance, then (a) E e = 2E a (b) E a = 2E e (c) E a = E e (d) none [2] 13. On rotating a point charge having a charge q around a charge Q in a circle of radius r. The work done will be (a) q × 2 pr (b) r Q 2 2 p × (c) zero (d) Q/ e 0 r 14. In the electric field of a point charge q, a certain charge is caller from point A to B, C D and E. (a) Is least along the path AB (b) Is least along the path AD (c) Is zero along all the paths AB, AC, AD and AE (d) Is least along AE 15. Four metallic plates each with a surface area of one side A are placed at a distance ‘d’ from each other. The plates are connected as shown in the circuit diagram. Then the capacitance of the system between ‘a’ and ‘b’ is (a) d A 3 0 e (b) d A 2 0 e (c) d 3 A 2 0 e (d) d 2 A 3 0 e 16. The V-I graph for a conductor at temperature T 1 and T 2 are as shown in the figure, (T 2 – T 1 ) is proportional to : (a) ? ? 2 sin 2 cos (b) ? ? 2 sin 2 sin (c) ? ? 2 sin 2 cot (d) ? ? 2 sin 2 tan 17. In the given circuit, find equivalent resistance between points M and N : (a) infinity (b) 2/3 r 0 (c) zero (d) none of these 18. A battery of cells with an e.m.f. 3V and internal resistance 1/4 ? is connected to a circuit consisting four resistances, R 1 = 1 ?, R 2 = 3 ?, R 3 = 1.5 ? and R 4 = 0.75 ? connected as shown in the figure. What is the current in unbranched arm ? (a) 3A (b) 6A (c) 1.5A (d) 2A 19. A cable of resistance 10 ? carries electric power from a generator producing 250 kW at 10000 volt. The current in the cable is (a) 25 A (b) 250A (c) 100 A (d) 1000A 20. 100 watt and 200 watt, two bulbs rating at 220 volts are connected in series. On supplying 220 volts, the consumption of power will be (a) 33 watt (b) 66 watt (c) 100 watt (d) 300 watt 21. Standard resistance coils are made of (a) Copper (b) Manganin (c) Platinum (d) Nichrome 22. Two heating coils, one of fine wire and the other of thick wire of the same material and of the same length are connected in series and in parallel. Which of the following is correct ? (a) in series fine wire liberates more energy while in parallel thick wire will liberate more energy (b) in series fine wire liberates less energy while in parallel thick wire will liberate more energy (c) Both will liberate equally (d) In series the thick wire will liberate more while in parallel it will liberate less energy 23. An electric bulb is rated 220 volt and 100 watt. Power consumed by it when operated on 110 volt is (a) 50 watt (b) 75 watt Page 3 [1] Test - 02 (Electrostatics & Current Electricity) 1. Coulomb’s law is true for : (a) atomic distances (= 10 -11 m) (b) nuclear distances (= 10 -15 m) (c) charged as well as uncharged particles (d) all the distances but for point object 2. Two conducting spheres of radii r 1 and r 2 are equal charged. The ratio of their charges is : (a) r 1 /r 2 (b) r 2 /r 1 (c) 2 2 2 1 r / r (d) 2 1 2 2 r / r 3. Three identical point charges, as shown are placed at the vertices of an isosceles right angles triangle. Which of the numbered vectors coincides in direction with the electric field at the mid-point M of the hypotenuse : (a) 1 (b) 2 (c) 3 (d) 4 4. The figure gives the electric potential V as a function of distance through five regions on x-axis. Which of the following is true for the electric field E in these regions : (a) E 1 > E 2 > E 3 > E 4 > E 5 (b) E 1 = E 3 = E 5 and E 2 < E 4 (c) E 2 = E 4 = E 5 and E 1 < E 3 (d) E 1 < E 2 < E 3 < E 4 < E 5 5. The capacity of a parallel plate air capacitor is 10 µF and it is given a charge 40 µC. The electrical energy stored in the capacitor in ergs is : (a) 80 × 10 6 (b) 800 (c) 8000 (d) 20000 6. Separation between the plates of a parallel plate capacitor is d and the area of each plate is A. When a slab of material of dielectric constant k and thickness t (t < d) introduced between the plates, its capacitance becomes : (a) ? ? ? ? ? ? - + e k 1 1 t d A 0 (b) ? ? ? ? ? ? + + e k 1 1 t d A 0 (c) ? ? ? ? ? ? - - e k 1 1 t d A 0 (d) ? ? ? ? ? ? + - e k 1 1 t d A 0 7. Can a condenser be given any amount of charge : (a) Yes (b) No (c) Depends on its shape (d) Depends on dielectric 8. In the figure bellows, what is the potential difference between the point A and B and between B and C respectively in steady state (a) V AB = 100volts. V BC = 100 volts (b) V AB = 75volts. V BC = 25 volts (c) V AB = 25volts. V BC = 75 volts (d) V AB = 50volts. V BC = 50 volts 9. A light bulb, a capacitors and a battery are connected together as shown here, with switch s initially open. When the switch S is closed, which one of the following is true ? (a) the bulb will light up for an instant when the capacitors starts charging (b) the bulb will light up when the capacitor is fully charged (c) the bulb will not light up at all (d) the bulb will light up and go off at regular internals 10. What air is replaced by dielectric medium of constant k, the maximum force of attraction between two charges separated by a distance (a) Decreases k times (b) Remains unchanged (c) Inreases k times (d) Increases k –1 time 11. The electric potential V is given as a function of distance × (metre) by V = (5x 2 + 10x – 9) volt. Value of electric field at x = 1m is (a) 20 V/m (b) 6 V/m (c) 11 V/m (d) –23 V/m 12. If E a be the electric field strength of a short dipole at a point on its axial line and E e that on the equatorial line at the same distance, then (a) E e = 2E a (b) E a = 2E e (c) E a = E e (d) none [2] 13. On rotating a point charge having a charge q around a charge Q in a circle of radius r. The work done will be (a) q × 2 pr (b) r Q 2 2 p × (c) zero (d) Q/ e 0 r 14. In the electric field of a point charge q, a certain charge is caller from point A to B, C D and E. (a) Is least along the path AB (b) Is least along the path AD (c) Is zero along all the paths AB, AC, AD and AE (d) Is least along AE 15. Four metallic plates each with a surface area of one side A are placed at a distance ‘d’ from each other. The plates are connected as shown in the circuit diagram. Then the capacitance of the system between ‘a’ and ‘b’ is (a) d A 3 0 e (b) d A 2 0 e (c) d 3 A 2 0 e (d) d 2 A 3 0 e 16. The V-I graph for a conductor at temperature T 1 and T 2 are as shown in the figure, (T 2 – T 1 ) is proportional to : (a) ? ? 2 sin 2 cos (b) ? ? 2 sin 2 sin (c) ? ? 2 sin 2 cot (d) ? ? 2 sin 2 tan 17. In the given circuit, find equivalent resistance between points M and N : (a) infinity (b) 2/3 r 0 (c) zero (d) none of these 18. A battery of cells with an e.m.f. 3V and internal resistance 1/4 ? is connected to a circuit consisting four resistances, R 1 = 1 ?, R 2 = 3 ?, R 3 = 1.5 ? and R 4 = 0.75 ? connected as shown in the figure. What is the current in unbranched arm ? (a) 3A (b) 6A (c) 1.5A (d) 2A 19. A cable of resistance 10 ? carries electric power from a generator producing 250 kW at 10000 volt. The current in the cable is (a) 25 A (b) 250A (c) 100 A (d) 1000A 20. 100 watt and 200 watt, two bulbs rating at 220 volts are connected in series. On supplying 220 volts, the consumption of power will be (a) 33 watt (b) 66 watt (c) 100 watt (d) 300 watt 21. Standard resistance coils are made of (a) Copper (b) Manganin (c) Platinum (d) Nichrome 22. Two heating coils, one of fine wire and the other of thick wire of the same material and of the same length are connected in series and in parallel. Which of the following is correct ? (a) in series fine wire liberates more energy while in parallel thick wire will liberate more energy (b) in series fine wire liberates less energy while in parallel thick wire will liberate more energy (c) Both will liberate equally (d) In series the thick wire will liberate more while in parallel it will liberate less energy 23. An electric bulb is rated 220 volt and 100 watt. Power consumed by it when operated on 110 volt is (a) 50 watt (b) 75 watt [3] (c) 90 watt (d) 25 watt 24. All bulbs in the figure are identical. Which bulb posses maximum brightness ? (a) Only bulb marked 1 (b) Only bulb marked 2 (c) Bulb marked 3 and 4 (d) bulb marked 1 and 5 25. In the figure shown , the potential difference between C and B is (a) 2.5 V (b) 5.0 V (c) 7.5 V (d) 10 V In every question a statement of ASSERTION is followed by a statement of REASON. Mark the correct answer out of the following choices: (a) If both ASSERTION and REASON are true and reason is the correct explanation of the assertion. (b) If both ASSERTION and REASON are true but reason is not the correct explanation of the assertion. (c) If ASSERTION is true but REASON is false. (d) If ASSERTION is false but REASON is true. 26. Assertion: When an object is negatively charged, its mass decreases. Reason: Electrons are negatively charged particles. 27. Assertion: Two conductors have identical volumes and they are given the same charge q. They will have the same potential. Reason: The potential of a conductor depends upon its charge. 28. Assertion: Force between two charges decreases when the charges are placed in water instead of air. Reason: Change of medium between the charges has no effect on the force between them. 29. Assertion: Conventional current is the flow of positive charge from the positive terminal of a battery to the negative terminal through the circuit. Reason: Conduction in metals is due to free electrons which are negatively charged. 30. Assertion: Standard resistance are made of constantan or mangnanin. Reason: Both constantan and mangnanin are alloys having a low temperature coefficient of resistance. ANSWER KEY 1 D 6 C 11 A 16 A 21 B 26 D 2 B 7 B 12 B 17 C 22 A 27 D 3 B 8 C 13 C 18 A 23 D 28 C 4 B 9 A 14 C 19 A 24 D 29 B 5 B 10 A 15 D 20 B 25 C 30 A Page 4 [1] Test - 02 (Electrostatics & Current Electricity) 1. Coulomb’s law is true for : (a) atomic distances (= 10 -11 m) (b) nuclear distances (= 10 -15 m) (c) charged as well as uncharged particles (d) all the distances but for point object 2. Two conducting spheres of radii r 1 and r 2 are equal charged. The ratio of their charges is : (a) r 1 /r 2 (b) r 2 /r 1 (c) 2 2 2 1 r / r (d) 2 1 2 2 r / r 3. Three identical point charges, as shown are placed at the vertices of an isosceles right angles triangle. Which of the numbered vectors coincides in direction with the electric field at the mid-point M of the hypotenuse : (a) 1 (b) 2 (c) 3 (d) 4 4. The figure gives the electric potential V as a function of distance through five regions on x-axis. Which of the following is true for the electric field E in these regions : (a) E 1 > E 2 > E 3 > E 4 > E 5 (b) E 1 = E 3 = E 5 and E 2 < E 4 (c) E 2 = E 4 = E 5 and E 1 < E 3 (d) E 1 < E 2 < E 3 < E 4 < E 5 5. The capacity of a parallel plate air capacitor is 10 µF and it is given a charge 40 µC. The electrical energy stored in the capacitor in ergs is : (a) 80 × 10 6 (b) 800 (c) 8000 (d) 20000 6. Separation between the plates of a parallel plate capacitor is d and the area of each plate is A. When a slab of material of dielectric constant k and thickness t (t < d) introduced between the plates, its capacitance becomes : (a) ? ? ? ? ? ? - + e k 1 1 t d A 0 (b) ? ? ? ? ? ? + + e k 1 1 t d A 0 (c) ? ? ? ? ? ? - - e k 1 1 t d A 0 (d) ? ? ? ? ? ? + - e k 1 1 t d A 0 7. Can a condenser be given any amount of charge : (a) Yes (b) No (c) Depends on its shape (d) Depends on dielectric 8. In the figure bellows, what is the potential difference between the point A and B and between B and C respectively in steady state (a) V AB = 100volts. V BC = 100 volts (b) V AB = 75volts. V BC = 25 volts (c) V AB = 25volts. V BC = 75 volts (d) V AB = 50volts. V BC = 50 volts 9. A light bulb, a capacitors and a battery are connected together as shown here, with switch s initially open. When the switch S is closed, which one of the following is true ? (a) the bulb will light up for an instant when the capacitors starts charging (b) the bulb will light up when the capacitor is fully charged (c) the bulb will not light up at all (d) the bulb will light up and go off at regular internals 10. What air is replaced by dielectric medium of constant k, the maximum force of attraction between two charges separated by a distance (a) Decreases k times (b) Remains unchanged (c) Inreases k times (d) Increases k –1 time 11. The electric potential V is given as a function of distance × (metre) by V = (5x 2 + 10x – 9) volt. Value of electric field at x = 1m is (a) 20 V/m (b) 6 V/m (c) 11 V/m (d) –23 V/m 12. If E a be the electric field strength of a short dipole at a point on its axial line and E e that on the equatorial line at the same distance, then (a) E e = 2E a (b) E a = 2E e (c) E a = E e (d) none [2] 13. On rotating a point charge having a charge q around a charge Q in a circle of radius r. The work done will be (a) q × 2 pr (b) r Q 2 2 p × (c) zero (d) Q/ e 0 r 14. In the electric field of a point charge q, a certain charge is caller from point A to B, C D and E. (a) Is least along the path AB (b) Is least along the path AD (c) Is zero along all the paths AB, AC, AD and AE (d) Is least along AE 15. Four metallic plates each with a surface area of one side A are placed at a distance ‘d’ from each other. The plates are connected as shown in the circuit diagram. Then the capacitance of the system between ‘a’ and ‘b’ is (a) d A 3 0 e (b) d A 2 0 e (c) d 3 A 2 0 e (d) d 2 A 3 0 e 16. The V-I graph for a conductor at temperature T 1 and T 2 are as shown in the figure, (T 2 – T 1 ) is proportional to : (a) ? ? 2 sin 2 cos (b) ? ? 2 sin 2 sin (c) ? ? 2 sin 2 cot (d) ? ? 2 sin 2 tan 17. In the given circuit, find equivalent resistance between points M and N : (a) infinity (b) 2/3 r 0 (c) zero (d) none of these 18. A battery of cells with an e.m.f. 3V and internal resistance 1/4 ? is connected to a circuit consisting four resistances, R 1 = 1 ?, R 2 = 3 ?, R 3 = 1.5 ? and R 4 = 0.75 ? connected as shown in the figure. What is the current in unbranched arm ? (a) 3A (b) 6A (c) 1.5A (d) 2A 19. A cable of resistance 10 ? carries electric power from a generator producing 250 kW at 10000 volt. The current in the cable is (a) 25 A (b) 250A (c) 100 A (d) 1000A 20. 100 watt and 200 watt, two bulbs rating at 220 volts are connected in series. On supplying 220 volts, the consumption of power will be (a) 33 watt (b) 66 watt (c) 100 watt (d) 300 watt 21. Standard resistance coils are made of (a) Copper (b) Manganin (c) Platinum (d) Nichrome 22. Two heating coils, one of fine wire and the other of thick wire of the same material and of the same length are connected in series and in parallel. Which of the following is correct ? (a) in series fine wire liberates more energy while in parallel thick wire will liberate more energy (b) in series fine wire liberates less energy while in parallel thick wire will liberate more energy (c) Both will liberate equally (d) In series the thick wire will liberate more while in parallel it will liberate less energy 23. An electric bulb is rated 220 volt and 100 watt. Power consumed by it when operated on 110 volt is (a) 50 watt (b) 75 watt [3] (c) 90 watt (d) 25 watt 24. All bulbs in the figure are identical. Which bulb posses maximum brightness ? (a) Only bulb marked 1 (b) Only bulb marked 2 (c) Bulb marked 3 and 4 (d) bulb marked 1 and 5 25. In the figure shown , the potential difference between C and B is (a) 2.5 V (b) 5.0 V (c) 7.5 V (d) 10 V In every question a statement of ASSERTION is followed by a statement of REASON. Mark the correct answer out of the following choices: (a) If both ASSERTION and REASON are true and reason is the correct explanation of the assertion. (b) If both ASSERTION and REASON are true but reason is not the correct explanation of the assertion. (c) If ASSERTION is true but REASON is false. (d) If ASSERTION is false but REASON is true. 26. Assertion: When an object is negatively charged, its mass decreases. Reason: Electrons are negatively charged particles. 27. Assertion: Two conductors have identical volumes and they are given the same charge q. They will have the same potential. Reason: The potential of a conductor depends upon its charge. 28. Assertion: Force between two charges decreases when the charges are placed in water instead of air. Reason: Change of medium between the charges has no effect on the force between them. 29. Assertion: Conventional current is the flow of positive charge from the positive terminal of a battery to the negative terminal through the circuit. Reason: Conduction in metals is due to free electrons which are negatively charged. 30. Assertion: Standard resistance are made of constantan or mangnanin. Reason: Both constantan and mangnanin are alloys having a low temperature coefficient of resistance. ANSWER KEY 1 D 6 C 11 A 16 A 21 B 26 D 2 B 7 B 12 B 17 C 22 A 27 D 3 B 8 C 13 C 18 A 23 D 28 C 4 B 9 A 14 C 19 A 24 D 29 B 5 B 10 A 15 D 20 B 25 C 30 A [4] SOLUTIONS 1. (d) Coulomb’s law is true for all distances small and large. 2. (b) As V = r 4 Q 0 ? p , Q = 4 p ? 0 rV. 3. (b) E A = electric field at M due to charge placed at A. E B = electric field at M due to charge placed at B. E C = electric field at M due to charge placed at C As seen from figure ? ? = C B E E So net electric field at M, E net =E A ; in the direction of vector 2 4. (b) electric field in the region 1, 3 and 5 is zero i.e E 1 = E 3 = E 5 5. Energy stored = C 2 q 2 = 6 2 6 10 10 2 ) 10 ( 40 40 - - × × × × = 80 × 10 –6 Joule = 800 erg 6. (c) 7. (b) Given charge depends on the capacity of condenser. 8. (c) 9. Initially when key is closed, the capacitor acts as short -circuit. So bulb will light up. But finally the capacitor becomes fully charged, so it will act as open circuit. So bulb will not glow. 10. (a) F ' = K F r q q 4 1 2 2 1 0 = pe . If F is the force in air, then F ' is less than F since K > 1. 11. E = - dx d dx dV - = (5x 2 + 10 x - 9) = - 10 x - 10 ? (E)x=1 = - 10 × 1 - 10 = - 20V/m 12. We have E a = 3 r kP 2 and E e = 3 r kP ? E a = 2E e 13. Because there is no change in the distance of two charges, so there is no change in electric potential. 14. ABCDE is equipotential surface because V = R 4 Q pe and R is same. As, work done= q ?V. so, work done = zero. 15. The given circuit can be redrawn as follows ? C eq = d 2 A 3 2 C 3 0 e = 16. According to ohm’s law, V = RI ; It means that slope of V -I graph give the resistance of conductor at a given temperature, Let R 1 = resistance of conductor at temperature T 1 ; Let R 1 = resistance of conductor at temperature T 2 ; According to graph, R 1 = tan ?; R 2 = R 1 [1 + a (T 2 - T 1 )] or cot ? = tan ? [1 + a (T 2 - T 1 )] or )] T T ( 1 [ tan cot 1 2 - a + = ? ? or a [T 2 - T 1 ] = 1 tan cot - ? ? or [T 2 - T 1 ] = ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? - ? a cos sin cos sin sin cos 1 2 2 ? [T 2 - T 1 ] = ? ? a 2 sin 2 cos 1 17. V M = V B = V D = V E = V F = V G = V 1 = V K = V N ? V M - V N = 0 or IR eq = 0 ? R eq = 0 18. ? x = R 4 + ? = + 5 . 1 R R R R 2 1 2 1 and y = ? = + 75 . 0 R x xR 3 3 ? Current in an unbranched circuit = A 3 25 . 0 75 . 0 3 = + 19. Since P = VI ? I = A 25 10000 250000 V P = = 20. r 1 = ? = = ? = 242 200 ) 220 ( r , 484 100 ) 220 ( 2 2 2 ? R = r 1 + r 2 = 726 ? ? Power consumed = watt 66 726 48400 726 ) 200 ( 2 = = 21. Due to high resistivity and low temperature coefficient. 22. In series total resistance R is maximum (thin). So P = i 2 R In parallel, total resistance R is minimum (thick). So P = R V 2 Page 5 [1] Test - 02 (Electrostatics & Current Electricity) 1. Coulomb’s law is true for : (a) atomic distances (= 10 -11 m) (b) nuclear distances (= 10 -15 m) (c) charged as well as uncharged particles (d) all the distances but for point object 2. Two conducting spheres of radii r 1 and r 2 are equal charged. The ratio of their charges is : (a) r 1 /r 2 (b) r 2 /r 1 (c) 2 2 2 1 r / r (d) 2 1 2 2 r / r 3. Three identical point charges, as shown are placed at the vertices of an isosceles right angles triangle. Which of the numbered vectors coincides in direction with the electric field at the mid-point M of the hypotenuse : (a) 1 (b) 2 (c) 3 (d) 4 4. The figure gives the electric potential V as a function of distance through five regions on x-axis. Which of the following is true for the electric field E in these regions : (a) E 1 > E 2 > E 3 > E 4 > E 5 (b) E 1 = E 3 = E 5 and E 2 < E 4 (c) E 2 = E 4 = E 5 and E 1 < E 3 (d) E 1 < E 2 < E 3 < E 4 < E 5 5. The capacity of a parallel plate air capacitor is 10 µF and it is given a charge 40 µC. The electrical energy stored in the capacitor in ergs is : (a) 80 × 10 6 (b) 800 (c) 8000 (d) 20000 6. Separation between the plates of a parallel plate capacitor is d and the area of each plate is A. When a slab of material of dielectric constant k and thickness t (t < d) introduced between the plates, its capacitance becomes : (a) ? ? ? ? ? ? - + e k 1 1 t d A 0 (b) ? ? ? ? ? ? + + e k 1 1 t d A 0 (c) ? ? ? ? ? ? - - e k 1 1 t d A 0 (d) ? ? ? ? ? ? + - e k 1 1 t d A 0 7. Can a condenser be given any amount of charge : (a) Yes (b) No (c) Depends on its shape (d) Depends on dielectric 8. In the figure bellows, what is the potential difference between the point A and B and between B and C respectively in steady state (a) V AB = 100volts. V BC = 100 volts (b) V AB = 75volts. V BC = 25 volts (c) V AB = 25volts. V BC = 75 volts (d) V AB = 50volts. V BC = 50 volts 9. A light bulb, a capacitors and a battery are connected together as shown here, with switch s initially open. When the switch S is closed, which one of the following is true ? (a) the bulb will light up for an instant when the capacitors starts charging (b) the bulb will light up when the capacitor is fully charged (c) the bulb will not light up at all (d) the bulb will light up and go off at regular internals 10. What air is replaced by dielectric medium of constant k, the maximum force of attraction between two charges separated by a distance (a) Decreases k times (b) Remains unchanged (c) Inreases k times (d) Increases k –1 time 11. The electric potential V is given as a function of distance × (metre) by V = (5x 2 + 10x – 9) volt. Value of electric field at x = 1m is (a) 20 V/m (b) 6 V/m (c) 11 V/m (d) –23 V/m 12. If E a be the electric field strength of a short dipole at a point on its axial line and E e that on the equatorial line at the same distance, then (a) E e = 2E a (b) E a = 2E e (c) E a = E e (d) none [2] 13. On rotating a point charge having a charge q around a charge Q in a circle of radius r. The work done will be (a) q × 2 pr (b) r Q 2 2 p × (c) zero (d) Q/ e 0 r 14. In the electric field of a point charge q, a certain charge is caller from point A to B, C D and E. (a) Is least along the path AB (b) Is least along the path AD (c) Is zero along all the paths AB, AC, AD and AE (d) Is least along AE 15. Four metallic plates each with a surface area of one side A are placed at a distance ‘d’ from each other. The plates are connected as shown in the circuit diagram. Then the capacitance of the system between ‘a’ and ‘b’ is (a) d A 3 0 e (b) d A 2 0 e (c) d 3 A 2 0 e (d) d 2 A 3 0 e 16. The V-I graph for a conductor at temperature T 1 and T 2 are as shown in the figure, (T 2 – T 1 ) is proportional to : (a) ? ? 2 sin 2 cos (b) ? ? 2 sin 2 sin (c) ? ? 2 sin 2 cot (d) ? ? 2 sin 2 tan 17. In the given circuit, find equivalent resistance between points M and N : (a) infinity (b) 2/3 r 0 (c) zero (d) none of these 18. A battery of cells with an e.m.f. 3V and internal resistance 1/4 ? is connected to a circuit consisting four resistances, R 1 = 1 ?, R 2 = 3 ?, R 3 = 1.5 ? and R 4 = 0.75 ? connected as shown in the figure. What is the current in unbranched arm ? (a) 3A (b) 6A (c) 1.5A (d) 2A 19. A cable of resistance 10 ? carries electric power from a generator producing 250 kW at 10000 volt. The current in the cable is (a) 25 A (b) 250A (c) 100 A (d) 1000A 20. 100 watt and 200 watt, two bulbs rating at 220 volts are connected in series. On supplying 220 volts, the consumption of power will be (a) 33 watt (b) 66 watt (c) 100 watt (d) 300 watt 21. Standard resistance coils are made of (a) Copper (b) Manganin (c) Platinum (d) Nichrome 22. Two heating coils, one of fine wire and the other of thick wire of the same material and of the same length are connected in series and in parallel. Which of the following is correct ? (a) in series fine wire liberates more energy while in parallel thick wire will liberate more energy (b) in series fine wire liberates less energy while in parallel thick wire will liberate more energy (c) Both will liberate equally (d) In series the thick wire will liberate more while in parallel it will liberate less energy 23. An electric bulb is rated 220 volt and 100 watt. Power consumed by it when operated on 110 volt is (a) 50 watt (b) 75 watt [3] (c) 90 watt (d) 25 watt 24. All bulbs in the figure are identical. Which bulb posses maximum brightness ? (a) Only bulb marked 1 (b) Only bulb marked 2 (c) Bulb marked 3 and 4 (d) bulb marked 1 and 5 25. In the figure shown , the potential difference between C and B is (a) 2.5 V (b) 5.0 V (c) 7.5 V (d) 10 V In every question a statement of ASSERTION is followed by a statement of REASON. Mark the correct answer out of the following choices: (a) If both ASSERTION and REASON are true and reason is the correct explanation of the assertion. (b) If both ASSERTION and REASON are true but reason is not the correct explanation of the assertion. (c) If ASSERTION is true but REASON is false. (d) If ASSERTION is false but REASON is true. 26. Assertion: When an object is negatively charged, its mass decreases. Reason: Electrons are negatively charged particles. 27. Assertion: Two conductors have identical volumes and they are given the same charge q. They will have the same potential. Reason: The potential of a conductor depends upon its charge. 28. Assertion: Force between two charges decreases when the charges are placed in water instead of air. Reason: Change of medium between the charges has no effect on the force between them. 29. Assertion: Conventional current is the flow of positive charge from the positive terminal of a battery to the negative terminal through the circuit. Reason: Conduction in metals is due to free electrons which are negatively charged. 30. Assertion: Standard resistance are made of constantan or mangnanin. Reason: Both constantan and mangnanin are alloys having a low temperature coefficient of resistance. ANSWER KEY 1 D 6 C 11 A 16 A 21 B 26 D 2 B 7 B 12 B 17 C 22 A 27 D 3 B 8 C 13 C 18 A 23 D 28 C 4 B 9 A 14 C 19 A 24 D 29 B 5 B 10 A 15 D 20 B 25 C 30 A [4] SOLUTIONS 1. (d) Coulomb’s law is true for all distances small and large. 2. (b) As V = r 4 Q 0 ? p , Q = 4 p ? 0 rV. 3. (b) E A = electric field at M due to charge placed at A. E B = electric field at M due to charge placed at B. E C = electric field at M due to charge placed at C As seen from figure ? ? = C B E E So net electric field at M, E net =E A ; in the direction of vector 2 4. (b) electric field in the region 1, 3 and 5 is zero i.e E 1 = E 3 = E 5 5. Energy stored = C 2 q 2 = 6 2 6 10 10 2 ) 10 ( 40 40 - - × × × × = 80 × 10 –6 Joule = 800 erg 6. (c) 7. (b) Given charge depends on the capacity of condenser. 8. (c) 9. Initially when key is closed, the capacitor acts as short -circuit. So bulb will light up. But finally the capacitor becomes fully charged, so it will act as open circuit. So bulb will not glow. 10. (a) F ' = K F r q q 4 1 2 2 1 0 = pe . If F is the force in air, then F ' is less than F since K > 1. 11. E = - dx d dx dV - = (5x 2 + 10 x - 9) = - 10 x - 10 ? (E)x=1 = - 10 × 1 - 10 = - 20V/m 12. We have E a = 3 r kP 2 and E e = 3 r kP ? E a = 2E e 13. Because there is no change in the distance of two charges, so there is no change in electric potential. 14. ABCDE is equipotential surface because V = R 4 Q pe and R is same. As, work done= q ?V. so, work done = zero. 15. The given circuit can be redrawn as follows ? C eq = d 2 A 3 2 C 3 0 e = 16. According to ohm’s law, V = RI ; It means that slope of V -I graph give the resistance of conductor at a given temperature, Let R 1 = resistance of conductor at temperature T 1 ; Let R 1 = resistance of conductor at temperature T 2 ; According to graph, R 1 = tan ?; R 2 = R 1 [1 + a (T 2 - T 1 )] or cot ? = tan ? [1 + a (T 2 - T 1 )] or )] T T ( 1 [ tan cot 1 2 - a + = ? ? or a [T 2 - T 1 ] = 1 tan cot - ? ? or [T 2 - T 1 ] = ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? - ? a cos sin cos sin sin cos 1 2 2 ? [T 2 - T 1 ] = ? ? a 2 sin 2 cos 1 17. V M = V B = V D = V E = V F = V G = V 1 = V K = V N ? V M - V N = 0 or IR eq = 0 ? R eq = 0 18. ? x = R 4 + ? = + 5 . 1 R R R R 2 1 2 1 and y = ? = + 75 . 0 R x xR 3 3 ? Current in an unbranched circuit = A 3 25 . 0 75 . 0 3 = + 19. Since P = VI ? I = A 25 10000 250000 V P = = 20. r 1 = ? = = ? = 242 200 ) 220 ( r , 484 100 ) 220 ( 2 2 2 ? R = r 1 + r 2 = 726 ? ? Power consumed = watt 66 726 48400 726 ) 200 ( 2 = = 21. Due to high resistivity and low temperature coefficient. 22. In series total resistance R is maximum (thin). So P = i 2 R In parallel, total resistance R is minimum (thick). So P = R V 2 [5] 23. Resistance of the bulb = ? = × = 484 100 220 220 W V 2 . When connected with 110 V, then power consumed P’ = W 25 484 110 110 R V 2 = × = 24. Full battery current passes through both these bulbs. 25. Let the current in branch ACDA be I, then in closed circuit ACDBA I(50 + 100 = 50)= 10 ? I = 20 1 . Therefore , potential difference across CB = 20 1 (50 + 50 + 50)= 7.5 V. 26. (d) Assertion is false but reason is true. An object acquires negative charge when electrons are transferred to the object. The mass of the object will increase slightly because has a very small mass ( ~ 9 × 10 -31 kg). 27. (d) Assertion is false but reason is true. The potential of a conductor does not depend on the total charge only, it also depends on the distribution of the charge on the conductor. Conductors with identical volumes may have different shapes and hence different charge distributions. Therefore, the potential of the two conductors may or may not be same. 28. (c) Assertion is true but reason is false. Coulomb’s force between the two charges depends upon the medium in which the charges are placed. 2 2 1 0 r q q K 4 1 F ? p = . As K for water is greater than one, the force decreases. 29. (b) Both assertion and reason are true but reason is not the correct explanation of the assertion. Current is defined as the amount of charge moving through a conductor per unit time. It is measured in Amperes (= coulomb/second). The direction of current is conventionally taken as the direction of flow of positive charge, though positive charges do not flow through the circuit. When a battery is connected to a circuit, it is the negative charges from the negative terminal of the battery which move across to the positive terminal through the electrical circuit. The assertion is a correct statement according to the accepted convention for the definition of current and as such required no reason. The given reason correctly explains the conduction of current in metals. Atoms of an element contain electrons orbiting the nucleus. The inner electrons are lightly bound whereas the electrons in the outer orbits are loosely bound and are easily separated from the nucleus. The movement of these free electrons constitutes the current and hence the conduction in metals. 30. (a) Both assertion and reason are true and reason is the correct explanation of the assertion. A standard resistance should not be easily affected by changes in temperature. Its value must be same over a wide range of temperature or at most vary only slightly with large variation of temperature. According to R t = R 0 (1 + aT) this is possible if a is small. As temperature coefficient of resistance a, for constantan and manganin is low, these alloys are used for making standard resistances.Read More

Offer running on EduRev: __Apply code STAYHOME200__ to get INR 200 off on our premium plan EduRev Infinity!