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MCQ’S TEST
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CLASS 12 PHYSICS LESSON - 1 ELECTRIC CHARGES AND FIELD OBJECTIVE QUESTIONS MCQ’S TEST
1. Which of the following methods can be used to charge a metal sphere positively without touching it? Select the most appropriate.
A. Rub it with a piece of fur.
B. Connect the positive terminal of a battery and float the other end of the battery. C. Rub it with a piece of silk.
D. Bring a negatively charged rod near the sphere and touch it to ground for a short while. Answer - D
Explanation -
This can be possible by induction, if a negative charge rod is placed near the sphere (at a distance not in touch) than it attracts positive charge inside the sphere towards its side and the negative charges collected on other side and when the surface of sphere connected to earth than the negative charge goes to earth and the sphere remain positively charged.
2. If 109 electrons move out of a body to another body every second, how much time is approximately required to get a total charge of 1C on the other body?
A. 200 years
B. 180 years
C. 220 years
D. 120 years
Answer - C
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3. Electric charge is a property of
A. particles such as atoms, ions and electrons
B. neutrons only
C. electrons only
D. protons only
Answer - A
Explanation - Every matter is made up of atoms which contains protons, electrons and neutrons. Protons are +ve charged particles and electrons are -ve charged particles. Because of electric charge these particles experience a force in electrical fields.
4. Electric charges are of
A. 5 types
B. 2 types
C. 3 types
D. 4 types
Answer - B
Explanation - Two types
Positive charge — deficiency of electrons i.e. if a body loses electrons, it will be positively charged. Negative charge — excess of electrons i.e. if a body gains electrons, it will be negatively charged
5. Conservation of charges in tribo electric charging
A. implies both are positively charged
B. implies both are negatively charged
C. implies one is positively charged and the other is negatively charged
D. implies half are positively charged and other half are neutral
Answer - C
Explanation - implies one is positively charged and the other is negatively charged.
6. Two positive charges
A. repel each other
B. attract each other
C. none of these
D. attract each other at times and repel at other times
Answer - A
Explanation - According to Coulomb's law, unlike charges, they always attract each other while charges always repel each other. So two positive charges repel each other.
7. Charge is quantized means
A. charge cannot take any arbitrary values, but only values that are integral multiples of the fundamental charge
B. charges can take any discontinuous values
C. charges can take discrete values that are multiples of charge on neutron
D. charges can take any continuous values
Answer - A
Explanation - Total charge transferred from one body to another can be calculated by the number of electrons it is known as quantisation of charge given by q = ±ne, where n = number of electrons, which should be an integer.
8.Ionization of a neutral atom is the
A. only gain of one or more electrons
B. gain or loss of one or more electrons
C. only gain of one or more protons
D. only gain of one or more neutrons
Answer - B
Explanation - It is not possible to remove or add protons to atoms, but electrons can be added or removed by an atom easily so charge can be developed on an atom by removing or adding electrons. By adding electrons it becomes negatively charged, by removing electrons it becomes positively charged.
9. Electrostatic force is the force exerted by
A. one charge on another when the two are at rest in a given frame of reference B. an electron on a neutron
C. one charge on another when the two are accelerating in a given frame of reference D. one charge on another when the two are moving in a given frame of reference
Answer - A
Explanation - Electrostatics means charges at rest,or relatively at rest so this force can be applicable only when charge produces an electric field which is constant which is possible only when charges are at rest or relatively at rest.
10. Conductors are materials that allow
A. only random movement of electrons
B. movement of electrons
C. movement of neutrons
D. movement of protons
Answer - B
Explanation - Conductors are materials that permit electrons to flow freely from particle to particle. An object made of a conducting material will permit charge to be transferred across the entire surface of the object.
In conductors some electrons are unpaired, so these electrons can move freely.
11. In charging by Induction, a metallic object is charged
A. by rubbing it with silk
B. by touching with a charged object
C. by bringing a charged object near it
D. by rubbing it with fur
Answer - C
Explanation - If a charged object is placed near an uncharged object, then redistribution of charge takes place in an uncharged object and if we will earth one surface of an uncharged object then one charge goes to earth and another charge spread on its surface and it becomes charged
12. The unit of charge is
A. ampere
B. volt
C. ohm
D. coulomb
Answer - D
Explanation - The SI unit of quantity of electric charge is the coulomb, which is equivalent to about 6.242×1018 e (e is the charge of a proton).
13. Electric field at a point is defined as
A. electric force experienced by a charge at that point
B. electric force experienced by two charges at that point
C. electric force per unit charge experienced by a unit charge at that point
D. electric force experienced by a dipole at that point
Answer - C
Explanation - Electric field intensity of a charge at a point is given by the force exerted by that charge on test charge or unit charge at that point
That is, the electric field intensity of charge q is E=Fq0
14. According to superposition of electric fields, the electric field of any combination of charges is the
A. scalar sum of the fields caused by the individual charges
B. vector sum of the individual charges
C. vector sum of the fields caused by the individual charges
D. cross product of the individual fields
Answer - A
Explanation - When several electric fields are working on single charge then the total electric field intensity on that charge is given by the vector sum of all electric field intensities E⃗ =E⃗ 1+E⃗ 2+E⃗ 3+…