Chapter # 13 Current Electricity

PHYSICS

CHAPTER # 13 Current Electricity

1. 2. 4. 5. 6. 7. 8. 9. 10.

11. 12. 13. 14. be: 15. 16.

17. 18. 19.

Rate of flow of charge through the surface is known as: a) Charge b) Electric current c) Ampere d) Coulomb The SI unit of current is: a) Volt b) Coulomb c) Ampere d) None of these Free electrons are: a) Loosely bound b) Tightly bound c) Fixed d) None of these In liquids and gases, the current is due to the motion of: a) Positive charges b) Negative charges c) Both positive and negative charges d) None of these Conventional current (I) is due to the motion of: a) Flow of positive charge b) Flow of negative charge c) Flow of neutron d) None of these The direction of conventional current in a circuit is: a) From negative to positive b) From positive to negative c) From negative to negative d) From positive to positive One advantage of conventional direction of current is that current flows from: a) High potential to low potential b) Low potential to high potential c) Negative potential to positive potential d) None of these The average velocity gained by the electrons in a conductor placed in an electric field is called: a) Variable velocity b) Phase velocity c) Drift velocity d) Instantaneous velocity Electronic or electric current ‘I’ in a conductor is defined by the relation: t Q Q a) I = b) I = t c) I = Qt d) None of these Ampere is a current in which charges flow across any cross-section at the rate of: a) 2C/S b) 3 CS-1 -1 c) CS d) CS-2 Current per unit area is called: a) Current density b) Electric charge c) Potential difference d) Resistance The SI unit of current density is: a) m2/A b) A/m2 2 c) m A d) mA2 If one ampere current flows through 2m long conductor, the charge flow through this in one hour will a) 2 C b) 120 C c) 3600 C d) 7200 C The relation V = IR represents: a) Coulomb’s law b) Ohm’s law c) Ampere law d) None of these “In an electrical circuit, the potential difference across a conductor is directly proportional to the current flowing through it, provided the temperature of the conductor remains the same”. It is known as: a) Ampere’s law b) Coulomb’s law c) Ohm’s law d) None of these Measure of the opposition to flow of free electrons is knows as: a) Conductance b) Charge c) Current d) Resistance The SI unit of resistance is: a) Coulomb b) Ohm c) Volt d) Ampere The graphical representation of Ohm’s law is: a) Hyperbola b) Parabola c) Straight line d) Ellipse

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PHYSICS

CHAPTER # 13 Current Electricity

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22. 23. 24. 25.

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31. 32. 33.

Ohm is defined as: a) VA-1 b) VC-1 -1 c) AV d) CV-1 If potential difference across the conductor is one volt and one ampere current is flowing, then resistance of the conductor is: a) One Farad b) One Ohm c) One Coulomb d) One Ampere Resistance of a conductor depends upon: a) The potential difference between its ends b) The nature of material of the conductor c) The dimension of conductor d) All of these The reciprocal of the resistance of a conductor is called: a) Specific resistance b) Current c) Conductance d) Effective resistance If the resistance of the conductor is increased then current will: a) Increase b) Decrease c) Remain the same d) First increase and then decrease When the temperature of a metallic conductor is increased its resistance: a) Always decreases b) Always increases c) May increase or decrease d) Remains the same If A is area of cross-section of a conductor and L is the length of the conductor, then resistivity “  ” of a conductor is given by the relation: RA L   a) = L b) = RA LA A   R R c) = d) = L The resistance of a conductor of length ‘L’, cross-sectional area ‘A’ and resistivity ‘  ’ is given by: LA L  a) R = b) R = A L  c) R = AL d) R = A The resistance of a conductor increases with the increase in its: a) Cross-sectional area b) Diameter c) Length d) Both diameter and cross-sectional area The resistance of a certain length of wire having diameter 5 mm is 10 Ohms. If diameter is changed to 10mm, the new resistance will become: a) 20 Ohms b) 40 Ohms c) 5 Ohms d) 2.5 Ohms Practical unit of resistivity is: a) Ohm-meter b) Ohm-ampere c) 1  -V d) 1  -F Reciprocal of resistivity is called: a) Inductance b) Specific resistance c) Conductivity d) Current Practical unit of conductivity is: a) (ohm-m)-1 b) Ohm-m c) (ohm-V)-1 d) (ohm-A)-1 The temperature co-efficient of resistivity is given by the relation: a)  =

 o  PT PT  T

c)  =

PT   o PT  T

T   o  T b)  = o T  o o  T d)

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D C B B A

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CHAPTER # 13 Current Electricity

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35.

36. 37. 38. 39. 40.

41. 42.

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48. 49. 50.

The temperature co-efficient of resistance is given by the relation: Ro  RT RT  Ro R T R T a)  = T b)  = o Ro RT RT Ro R T R T c)  = T d)  = T The change in resistivity per unit original resistivity (or resistance) per degree change in temperature is called: a) Resistance b) Conductance c) Temperature co-efficient of resistivity d) All of these The SI unit of the temperature co-efficient of resistivity of a material is: a) Ohm-m b) K c) K-1 d) Ohm The resistance of a conductor at absolute zero is: a) Zero b) Infinite c) Positive d) Negative A good electrical conductor has: a) Low resistivity and high conductivity b) High resistivity and low conductivity c) No resistivity and no conductivity d) All of these Resistivity of the typical metal increases: a) With increase in temperature b) With decrease in temperature c) With constant temperature d) None of these The resistivity of a class of elements at critical temperature “T c” falls to zero, such elements (or materials) are called: a) Semiconductors b) Superconductors c) Conductors d) Insulators The temperature at which the value of resistivity falls to zero is called: a) Lowest temperature b) Zero temperature c) Critical temperature d) Absolute zero temperature The phenomenon that the resistance of a metal falls exactly to zero at a few degrees above absolute zero is called: a) Conductivity b) Low conductivity c) Super-conductivity d) Low resistivity In a laboratory of Zurich, two scientists Bednorz and Mueller observed that certain ceramic materials exhibit super-conductivity at much higher temperature, that is at: a) T = 30 K b) T = 125 K c) T = 40 K d) T = 20 K New prepared ceramic materials have been found to be super-conductors even at: a) T = 30K b) T = 125 K c) T = 75 K d) T = 150 K When the resistors are connected in series, then: a) The total current through each is the same b) The voltage across each is the same c) The total resistance is the sum of reciprocals of the individuals d) The total resistance is the product of the individual resistors If resistors R1, R2, ….. Rn are connected in series, the equivalent resistance Re is given by: 1 1 1 1 1 R e R1 R 2 R 3 R a) = + + …..+ n b) Re = R1+R2+R3+ ….. Rn c) Re = R1R2R3….. Rn d) None of these Why should a resistance be introduced in a circuit in series deliberately? a) To increase current b) To decrease current c) To control current d) None of these Why should different resistance be added in series in a circuit? a) To increase voltage b) To decrease voltage c) To divide voltage d) None of these When the resistors are connected in series, the equivalent resistance is always: a) Greater than the greatest resistance in series b) Less than the largest resistance in series c) Equal to the greatest resistance in series d) Less than the smallest resistance in series

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CHAPTER # 13 Current Electricity

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If resistors R1, R2, ….. Rn are connected in parallel, the equivalent resistance ‘Re’ is given by: 1 1 1 1 1 R e R1 R 2 R 3 R a) = + + …..+ n b) Re = R1+R2+R3+ ….. Rn 1 1 1 1 R R R R a) Re = 1 + 2 + 3 …..+ n b) None of these In a house circuit, all electrical appliances are connected in parallel to each other between the line an neutral wires to get: a) Same current b) Same current and potential difference c) Different current but same potential difference d) Different current & different potential diff. When resistors are connected in parallel, the equivalent resistance is always: a) Greater than the sum of individual resistance b) Greater than the smallest resistance in the combination c) Less than the smallest resistance in the combination d) Equal to the sum of individual resistance Three resistors of resistance 2,3 and 6 Ohms are connected in parallel, their equivalent resistance is: a) 0.1 ohm b) 1.0 ohm c) 3 ohms d) 2 ohms Three resistors of resistance 2,3 and 6 Ohms are connected in series, their equivalent resistance will be: a) 0.1 ohm b) 1.0 ohm c) 6 ohms d) 11 ohms As the charge flows through the conductor energy is dissipated in the form of: a) Heat b) Light c) Solar energy d) None of these Power dissipated as heat in the conductor of resistance ‘R’ due to electric current ‘I’ is given by: a) P = I2R2 b) P = I2R R I2 2 c) P = R d) P = I Power dissipated in the form of ‘V’ and ‘I’ can be defined as: V a) P = VI b) P = I

V2 59.

2 2 c) P = I d) P = V Power dissipated in the form of ‘V’ and ‘R’ can be determined as: V V2 a) P = I b) P = R

62. 63. 64.

C

B D

A B

A

B

V2 d) P = I

2

61.

C

I2

V 60.

A

c) P = R Unit of power, Joule/second is called: a) Joule b) Volt c) Watt d) Newton If one ampere current flows through a resistor against potential difference of one volt, this is called: a) Ampere b) Watt c) Volt d) Joule Watt is equal to: a) Joule-coulomb b) Joule-second c) Joule/second d) None of these The practical unit of power is: a) Watt b) Kilowatt c) Joule d) None of these One kilowatt is equal to: a) 103 watts b) 106 watts 12 c) 10 watts d) None of these

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PHYSICS

CHAPTER # 13 Current Electricity

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68. 70. 72. 73. 74.

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79. 80. 81. 82. 83. 84.

Heat energy dissipated in resistors is defined as: a) VIt b) I2Rt c) Both a & b d) Neither a nor b The unit of electrical energy is: a) Kilowatt-hour b) Kilowatt c) Joule d) None of these Amount of energy delivered by the current in one hour when it supplies energy at the rate of 1000 J/s is known as: a) Joule b) Kwh c) Newton d) None of these 1 Kwh = _______: a) 3.6  106 J b) 3.6  108 J 6 c) 6.3  10 J d) 6.3  108 J A 1000 watt heater operates on a 220 volt line for one hour. The current passing through heater is: a) 15 A b) 7 A c) 5.4 A d) 4.5 A A 100 watt bulb is operated by 200 volt, the current flowing through the bulb is: a) 1 ampere b) 0.5 ampere c) Zero ampere d) 2 amperes The resistance of 60 watt bulb in a 120 volt line is: a) 30 ohms b) 120 ohms c) 240 ohms d) 60 ohms The devices which can maintain a potential difference between points to which they are attached are known as: a) Source of electricity b) Source of electromotive force (emf) c) Source of heat d) None of these The work per unit charge done by the source of emf in moving a charge around a closed loop is called: a) Electromotive force (emf) b) Potential difference c) Potential energy d) Kinetic energy The total energy expended per coulomb of electricity when charge is driven round a circuit is called: a) Electromotive source b) Electromotive force (emf) c) Potential energy d) Kinetic energy The electromotive force of a battery or cell is the voltage between its terminals when: a) The circuit is closed b) The circuit is open c) Its internal resistance is minimum d) Its internal resistance is maximum The electromotive force (emf) is defined by the relation: a) E = IR b) E = IQ W V q q c) E = d) E = When we connect two given cells in parallel the total emf of the combination is equal to: a) Zero b) Sum of emfs of the individual cells c) The emf of the small cell d) The emf of the large cell By electromotive force: a) Sound is produced b) Heat is produced c) Light is produced d) Current is produced Electric generators convert: a) Mechanical energy into electrical energy b) Electrical energy into mechanical energy c) Heat energy into electrical energy d) Kinetic energy into electrical energy Thermocouples convert: a) Electrical energy into heat energy b) Heat energy into electrical energy c) Kinetic energy into potential energy d) Light energy into electrical energy Photovoltaic cell converts: a) Light energy into electrical energy b) Heat energy into electrical energy c) Chemical energy into electrical energy d) None of these The unit of electromotive force is: a) Coulomb per second (ampere) b) Joule per second (watt) c) Joule per coulomb (volt) d) Coulomb per volt (farad)

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CHAPTER # 13 Current Electricity

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The source of emf converts some form of energy into: A a) Electrostatic potential (electrical) energy b) Kinetic energy c) Chemical energy d) Nuclear energy Electromotive force is closely related to: C a) Electric field intensity b) Magnetic flux density c) Potential difference d) None of these Batteries or cells convert: B a) Heat energy into electrical energy b) Chemical energy into electrical energy c) Nuclear energy into electrical energy d) Kinetic energy into electrical energy The emf of a source is equal to the potential difference across the terminals of the source when its A internal resistance is: a) Zero b) Infinite c) Zero or infinite d) None of these Terminal potential difference ‘Vt’ of a battery of internal resistance ‘r’ and emf ‘E’ is: A a) Vt = E - Ir b) Vt = E + Ir E c) Vt = EIr d) Vt = IR

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