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Electric Current

One coulomb of electrical charge is contributed by how many electrons?
1. 0.625 × 1019.
2. 1.6 × 1019.
3. 1019.
4. 1.6 × 1012.
Ans: 1
5 × 1016 electrons pass across the section of a conductor in 1 minutes and 20 seconds. The current is flowing
1. 0.1 mA.
2. 1 mA.
3. 10 mA.
4. 100 mA.
Ans: 1
An current of 6 A is same as
1. 6 Joule / second.
2. 6 Coulomb / second.
3. 6 Watt / second.
4. none of the above.
Ans: 2
Ampere - second is the unit of
1. conductance.
2. power.
3. energy.
4. charge.
Ans: 4
The current in a circuit follows the relation i = 100sinωt. If frequency is 25 Hz, how long will it take for thecurrent to rise to 50 A ?
1. 1 ms.
2. 3.33 ms.
3. 10 ms.
4. 20 ms.
Ans: 2
The equation of a current is given by i = Imsin2ωt. The frequency of the current in Hz is
1. ω ⁄ 2π.
2. ω ⁄ 2.
3. 2ω ⁄ π.
4. ω ⁄ π.
Ans: 4
The equation of alternating current is i = 42.4sin628t. Then the average value of current is
1. 42.42 A.
2. 27 A.
3. 38 A.
4. 22 A.
Ans: 2
If 1 A current is flowing through a series circuit having 100 resistors of each having resistance of 1 Ω. What will be the current in the circuit where, these 100 resistors are connected in parallel?
1. 10 A.
2. 100 A.
3. 1000 A.
4. 10000 A.
Ans: 4
In the figure shown, what will be the current passing through 2 Ω resistor ?
1. 0.25 A.
2. 0.75 A.
3. 0.5 A.
4. 1 A.
Ans: 1
A copper conductor of one square millimeter can safely carry an current of
1. 100 A.
2. 50 A.
3. 25 A.
4. 10 A.
Ans: 4
For carrying an current of 75 A an aluminium conductor should have a minimum cross-section of
1. 25 mm2.
2. 10 mm2.
3. 15 mm2.
4. 20 mm2.
Ans: 1
A copper wire of length l and diameter d has potential difference V applied across its two ends. The drift velocity is Vd. If the diameter of the wire is made d / 2, then the drift velocity becomes
1. Vd.
2. 4Vd.
3. Vd / 4.
4. Vd / 2.
Ans: 1
Mass of a proton is how many times greater than mass of an electron?
1. 184000.
2. 18400.
3. 1840.
4. 184.
Ans: 3
On which factors does the severity of electric shock depends ?
1. Only on pathway through the body.
2. Only on the type of supply ac/dc.
3. Only on magnitude of voltage.
4. All of above.
Ans: 4
Five coulomb of electrical charge is contributed by how many electrons?
1. 3.125 × 1019.
2. 1.6 × 1019.
3. 1019.
4. 1.6 × 1012.
Ans: 1
The transient current in a series AC circuit is given by
Find the initial current ?
1. 2 Amp.
2. 1 Amp.
3. 0 Amp.
4. 8734 Amp.
Ans: 2
Alternating current is found most suitable for
1. arc welding.
2. resistance welding.
3. gas welding.
4. electric arc welding.
Ans: 2
The rms value of a half wave rectified symmetrical square wave current of 2 A is given by
1. 0.707 A.
2. 1 A.
3. 1.414 A.
4. 1.732 A.
Ans: 3
How many coulombs of charge flows through a circuit carrying 5 A in 5 min?
1. 1500.
2. 150.
3. 15.
4. 1.
Ans: 1

The flow of current in solids is due to
1. electrons and ions
2. electrons.
3. atoms.
4. nucleus.
Ans: 2
Ampere second could be the unit of
1. power.
2. conductance.
3. charge.
4. energy.
Ans: 3
The drift velocity of electrons is
1. very small as compared to speed of light.
2. equal to speed of light.
3. almost equal to speed of light.
4. greater than speed of light.
Ans: 1
The charge on an electron is known to be 1.6 × 10-19coulomb. In a circuit the current flowing is 1 A. How many electrons will be flowing through the circuit in a second?
1. 1.6 × 1019.
2. 1.6 × 10-19.
3. 0.625 × 1019.
4. 0.625 × 1012.
Ans: 3
In gases the flow of current is due to
1. electrons only.
2. positive ions only.
3. negative ions only.
4. electrons, positive ions and negative ions only.
Ans: 4
An current of 5 A is same as
1. 5 J / C.
2. 5 C / Sec.
3. 5 V / C.
4. 5 W / C.
Ans: 2
An instrument which detects current is known as
1. voltmeter.
2. wattmeter.
3. galvanometer.
4. rheostat.
Ans: 3
Current flows in a circuit when
1. a switch is opened.
2. a switch is closed.
3. the switch is either open or closed.
4. there is no voltage.
Ans: 2
Eight-tenths coulomb passes a point in 4 s. The currentin amperes is
1. 1.6 A.
2. 2 A.
3. 16 A.
4. 0.2 A.
Ans: 4
An ammeter is an electrical instrument used to measure
1. voltage.
2. current.
3. resistance.
4. reluctance.
Ans: 2
The rate of flow an electric charge is known as
1. current.
2. voltage.
3. conductance.
4. power.
Ans: 1
The minimum requirement for causing flow of currentare
1. A voltage source, a resistor and a switch.
2. A voltage source and a conductor.
3. A power source an bulb.
4. A voltage source, a conductor, an ammeter and switch.
Ans: 2
Which of the following current is considered dangerous to the human body
1. 1 mA.
2. 50 mA.
3. 0.5 mA.
4. 25 mA.
Ans: 2
The ratio of voltage and electrical current in a closed circuit
1. increases.
2. varies.
3. falls.
4. remain constant.
Ans: 4
Current velocity through the copper conductor is
1. nearly 3 × 108 m/sec.
2. independent of the current strength.
3. the same as propagation velocity of electrical energy.
4. of order of few micro m/s.
Ans: 1
Which of the following statements is true?
1. A galvanometer with low resistance in parallel is a voltmeter.
2. A galvanometer with high resistance in parallel is a voltmeter.
3. A galvanometer with low resistance in series is an ammeter.
4. A galvanometer with high resistance in series is an ammeter.
Ans: 3
An electric bulb can be worked from
1. AC supply only.
2. DC supply only.
3. battery supply only.
4. all of these.
Ans: 4
Electric current passing through the circuit produces
1. magnetic effect.
2. thermal effect.
3. luminius effect.
4. all of above.
Ans: 4
When current passes through a metallic conductor, it temperature rises. This is due to
1. collisions between conduction electrons and atoms.
2. the release of conduction electrons from parent atoms.
3. mutual collisions between metal atoms.
4. mutual collisions between conducting electrons.
Ans: 1
If a parallel circuit is opened in the main line, the current
1. increases in the branch of the lowest resistance.
2. increases in each branch.
3. is zero in all branches.
4. is zero in the highest resistive branch.
Ans: 3

A conductor of length L has carrying current I passing through it, when it is placed parallel to strong magnetic field. The force experienced by the conductor will be
1. BIL.
2. BL2I.
3. BI2L.
4. zero.
Ans: 4
The force between two long parallel conductors is inversely proportional to
1. radius of conductors.
2. current in one conductor.
3. product of current in two conductors.
4. distance between the conductors.
Ans: 3
In the left hand rule, forefinger always represents
1. voltage.
2. current.
3. magnetic field.
4. direction of force on the conductor.
Ans: 1
A wire carrying current is bent in the form of a circular loop. Then the magnetic field around each portion of the wire will be
1. parallel to the plane of the wire.
2. perpendicular to the circumference of the wire.
3. parallel to half portion and perpendicular for the other half.
4. none of above.
Ans: 1
Cork Screw rule is used to find
1. direction of current.
2. direction of magnetic field.
3. direction of electric field.
4. direction of emf.
Ans: 1
Two long parallel conductors carry 100 A. If the conductors are separated by 20 mm, the force per meter of length of each conductor will be
1. 100 N.
2. 10 N.
3. 1 N.
4. 0.01 N.
Ans: 2
The field at any point on the axis of a current carrying coil will be
1. parallel to axis.
2. perpendicular to the axis.
3. at angle of 45° with the axis.
4. zero.
Ans: 3
Two straight parallel conductors carry equal currents in opposite direction. The force between them is
1. repulsive.
2. attractive.
3. zero.
4. none of above.
Ans: 1
While comparing magnetic field and electric circuits, the point of dissimilarity exists while considering
1. mmf and emf.
2. reluctance and resistance.
3. flux and current flow.
4. permeance and conductance.
Ans: 3
A wire 2.5 m long is bent into a square. An current of 100 A flowing through the wire will produce a magnetizing force at the center of the square, equal to
1. 72 AT / m.
2. 144 AT / m.
3. 196 AT / m.
4. 222 AT / m.
Ans: 2
Magnetism of a magnet can be destroyed by
1. heating.
2. hammering.
3. by inductive action of another magnet.
4. by all above methods.
Ans: 4
The change of cross sectional area of conductor inmagnetic field will affect
1. reluctance of conductor.
2. resistance of conductor.
3. (A) and (B) both in the same way.
4. none of above.
Ans: 3
Substance having permeability less than the permeability of free space, are known as
1. diamagnetic.
2. bipolar.
3. paramagnetic.
4. ferromagnetic.
Ans: 4
A point pole has a strength of 4π × 10-4 weber. The force in newtons on a point pole of 4π × 1.5 × 10-4weber placed at a distance of 10 cm from it will be
1. 20 N.
2. 15 N.
3. 7.5 N.
4. 3.75 N.
Ans: 1
Susceptibility is positive for
1. non magnetic substances.
2. diamagnetic substances.
3. ferromagnetic substances.
4. none of above.
Ans: 2
Biot-Savart's law states the relation between magnetic intensity and
1. filament current only.
2. surface current only.
3. volume current only.
4. (A), (B), and (C) are all correct.
Ans: 3
The bar magnet has
1. the dipole moment.
2. monopole moment.
3. (A) and (B) both.
4. none of above.
Ans: 1
The magnetisation and applied field in ferromagnetic materials are related
1. sinusoidally.
2. linearly.
3. non linearly.
4. parabolically.
Ans: 2
Temporary magnets are used in
1. loud speakers.
2. generators.
3. motors.
4. all of above.
Ans: 1
A degaussing is the process of
1. removing gases from materials.
2. removal of magnetic impurities.
3. demagnetising metallic parts.
4. remagnetising metallic parts.
Ans: 1

Almost the entire mass of an atom is concentrated in the
1. protons.
2. electrons.
3. neutrons.
4. nucleus.
Ans: 4
All ions of an element have the same
1. atomic number.
2. number of electrons.
3. number of protons.
4. both option A. and C.
Ans: 4
The mass of the atom is determined by
1. proton.
2. electrons.
3. neutron and proton.
4. electron and proton.
Ans: 3
The absolute charge of an electron is
1. - 1.6 × 10-19 C.
2. + 1.6 × 10-19 C.
3. 1.6 × 10-19 C.
4. none of above.
Ans: 1
The fixed circular paths around the nucleus are called
1. orbits.
2. orbitals.
3. mesons.
4. nucleus.
Ans: 1
According to the Bohr model, an electron gains or losses energy only by
1. moving faster or slower in an allowed orbit.
2. jumping from one allowed orbit to another.
3. being completely removed from an atom.
4. jumping from one atom to another atom.
Ans: 2
The number of rings in the Bohr model of any element is determined by what?
1. Column number on periodic table.
2. Atomic mass.
3. Row number on periodic table.
4. Atomic number.
Ans: 3
How many valence electrons would be found in an atom with the atomic number of 51?
1. 5.
2. 51.
3. 8.
4. none of above.
Ans: 1
The Bohr model of the atom
1. explained the color lines in the hydrogen spectrum.
2. could not explain the line spectrum of atoms larger than hydrogen.
3. had some made-up rules without explanations.
4. all of the above.
Ans: 1
Maximum number of electrons in a sub-shell with l = 3 and n = 4 is
1. 10.
2. 14.
3. 20.
4. 8.
Ans: 2
Which of the following statements is not part of Dalton's atomic theory?
1. All matter is composed of atoms.
2. Atoms can combine to form compounds.
3. Atoms of different elements are quite different.
4. An atom contains a dense central nucleus.
Ans: 4
Atoms with fewer than 4 valence electrons are
1. insulator.
2. semi-conductor.
3. conductor.
4. none of these.
Ans: 3
Atoms have no electric charge because they
1. have an equal number of charged and non charged particles.
2. have neutrons in their nuclei.
3. have an equal number of neutrons and protons.
4. have an equal number of electrons and protons.
Ans: 4
Two different isotopes of an element have different
1. numbers of neutrons.
2. numbers of electrons.
3. atomic number.
4. numbers of protons.
Ans: 1
What is the mass number of an element that has 19 protons, 19 electrons, and 20 neutrons?
1. 19.
2. 39.
3. 38.
4. 20.
Ans: 2
Which of the following statements is not true?
1. A s orbital can hold two electrons.
2. A d orbital can hold ten electrons.
3. A f orbital can hold three electrons.
4. A p orbital can hold six electrons.
Ans: 3
The drawback of Dalton's atomic structure is that, it says
1. the atoms can neither be created nor be destroyed.
2. unique nature of atom.
3. most of the volume of an atom is empty space.
4. none of these.
Ans: 1
The electron configuration of copper is
1. 1s2 , 2s2 2p6, 3s2 3p6 3d8, 4s1 4p2.
2. 1s2 , 2s2 2p6, 3s2 3p6 3d10, 4s1.
3. 1s2 , 2s2 2p6, 3s2 3p6 3d9, 4s2.
4. none of above.
Ans: 2
Silicon has
1. four valence electrons.
2. eight valence electrons.
3. two valence electrons.
4. none of above.
Ans: 1
The electron configuration of sulfur atom is
1. 2, 8, 6.
2. 1s2 , 2s2 2p6, 3s2 3p6.
3. 2, 8, 2.
4. none of these.
Ans: 1

The electron is lighter than a proton by a factor of about
1. 18.4.
2. 184.
3. 1840.
4. 18400.
Ans: 3
The charge of an electron is
1. - 1.602 × 10 - 19 Coulombs.
2. - 1.675 × 10 - 27 Coulombs.
3. - 1.672 × 10 - 27 Coulombs.
4. - 9.109 × 10 - 31 Coulombs.
Ans: 1
The mass of a proton is
1. 1.675 × 10 - 27 Kg.
2. 1.672 × 10 - 27 Kg.
3. 1.602 × 10 - 19 Kg.
4. 1.609 × 10 - 31 Kg.
Ans; 2
The mass of a neutron of atom is
1. 1.675 × 10 - 27 Kg.
2. 1.672 × 10 - 26 Kg.
3. 1.602 × 10 - 19 Kg.
4. 1.609 × 10 - 31 Kg.
Ans: 1
In Bohr’s model of atomic structure, the nucleus consists of
1. electrons.
2. electrons and protons.
3. protons and neutrons.
4. protons.
Ans: 3

The atomic radius in case of face centered cubic lattice is
1. a.
2. a / 2.
3. a / 3.
4. a / 4.
Ans: 2
The materials which exhibit the same elastic properties in all directions are called
1. isotropic.
2. isentropic.
3. inelastic.
4. visco elastic.
Ans: 1
Which of the following is the heaviest?
1. Molecule.
2. Atom.
3. Electron.
4. Proton.
Ans: 1
Germanium has
1. ionic bond.
2. covalent bond.
3. molecular bond.
4. metallic bond.
Ans: 2
Energy gap of conductor is
1. 1 - 2 eV.
2. 0 eV.
3. 5 - 8 eV.
4. 8 eV.
Ans: 2
Energy gap of semiconductor is approx
1. 1 eV.
2. 0 eV.
3. 5 - 8 eV.
4. > 8 eV .
Ans:1

Sri Neelakanteswara ITI