Electric Charge MCQ Quiz - Objective Question with Answer for Electric Charge - Download Free PDF

Ans.(4)

Sol.

The basic properties of electric charge are:

Charges are additive in nature.

Charge is a conserved quantity.

Quantization of charge.

The correct answer is Option 2: A charge static in space having zero speed.

Explanation:

Magnetic field: Produced only by charges in motion.

A static charge with zero speed generates only an electric field.

It does not produce a magnetic field because magnetic fields require moving charges.

The correct answer is - 1.6 × 10⁻¹⁰ C

Key Points

• Charge Calculation
  • The charge of an electron is -1.602 × 10⁻¹⁹ C.
  • When 10⁹ electrons are transferred from object A to object B, the total charge transferred is:
    • Charge = Number of electrons × Charge of one electron
    • Charge = 10⁹ × -1.602 × 10⁻¹⁹ C
    • Charge = -1.602 × 10⁻¹⁰ C
  • Since electrons are negatively charged, object A will lose a negative charge, making it positively charged with a charge of +1.602 × 10⁻¹⁰ C.

Additional Information

• Conservation of Charge
  • The principle of conservation of charge states that the total charge in an isolated system remains constant.
  • In this scenario, the total charge of the system before and after the transfer of electrons remains the same.
• Charging by Friction
  • When two objects are rubbed together, electrons are transferred from one object to another, leading to a charge imbalance.
  • The object losing electrons becomes positively charged, while the object gaining electrons becomes negatively charged.
• Fundamental Charge (e)
  • The charge of a single electron (e) is approximately -1.602 × 10⁻¹⁹ C.
  • This fundamental charge is a constant value used in various calculations involving electric charge and forces.

Concept:

For equilibrium, the net force acting on the body must be zero. This means the weight must be balanced by the electric force and buoyant force.

Explanation:

Volume of the sphere:

V = (4/3) × π × r³ = (4/3) × π × (0.5 × 10⁻²)³ = (4/3) × π × 125 × 10⁻⁹ = (5π/3) cm³

Net force equation:

8 × (5π/3) × g = 0.8 × (5π/3) × g + q × 600π

Rearranging:

12πg = 600πq

⇒ q = (2g × 10⁻⁶) = 2 × 10⁻⁵ C

The correct answer is Option (2): 2 × 10⁻⁵ C

The Correct answer is Gold-leaf electroscope.

Key Points

• The Gold-leaf electroscope is an instrument used for detecting and measuring electric charge.
• It consists of a vertical metal rod with two thin gold leaves attached at the bottom.
• When a charged object comes into contact with the metal rod, the charge gets transferred to the gold leaves.
• Due to like charges repelling, the gold leaves diverge, indicating the presence of electric charge.
• This apparatus is highly sensitive and can detect even small amounts of charge.
• It is widely used in physics experiments and educational demonstrations to show the presence of static electricity.

Additional Information

• Silver-leaf electroscope
  • No common apparatus named Silver-leaf electroscope exists in scientific literature or common usage.
• Platinum-leaf electroscope
  • Similar to the silver-leaf electroscope, no common apparatus named Platinum-leaf electroscope is known.
• Silver-rod electroscope
  • This term is not typically used to describe an electroscope. The most commonly used type is the gold-leaf electroscope due to its sensitivity.

Millikan's Oil drop experiment: 

• In this experiment, Milliken allowed charged tiny oil droplets to pass through a hole into an electric field.
• By varying the strength of the electric field the charge over an oil droplet was calculated, which always came as an integral value of charge on one electron.

Davisson-Gomer's experiment:

• Initially, the atomic models proposed by various scientists could only explain the particle nature of electrons but failed to explain their wave nature.
• In the year 1927 C.J. Davisson and L.H. Germer perform an experiment, which is known as Davisson Germer’s experiment by which they explain the wave nature of electrons through electron diffraction.

Compton scattering experiment:

• Compton effect is defined as the effect that is observed when x-rays or gamma rays are scattered on a material with an increase in wavelength.
• Arthur Compton studied this effect in the year 1922.
• During the study, Compton found that wavelength is not dependent on the intensity of incident radiation.
• It is dependent on the angle of scattering and on the wavelength of the incident beam.

Raman effect: Raman effect is defined as the scattering of photons by the excited molecules that are at higher energy levels.

CONCEPT:

• Electric charge: It is an intrinsic property of the elementary particles of matter which gives rise to electric force between various objects.
• It is a scalar quantity.
• SI unit of electric charge is coulomb (C).
• The total charge on the conductor is given by q = It, when current flows through the conductor for some time.

Where I = current and t = time

EXPLANATION:

• When a soap bubble is charged, then the charged particle will uniformly be distributed over the surface of the soap bubble.
• Hence the radius of the soap bubble will increase because the charged particles are uniformly distributed on the soap bubble and this will cause them to repel each other due to the electrostatic force. Therefore option 2 is correct.

Concept:

Electric charge(q): The property of matter which is responsible for electrostatic force is called an electric charge.

The SI unit of charge is coulomb (C).

The rate of flow of electric charge is called an electric current.

Charge (q) = current (I) × time (t)

Calculation:

Given that;

Current (I) = 0.5 A

Time (t) = 20 min = 20 × 60 sec = 1200 sec

CONCEPT:

• Charge: The property of matter that is responsible for electrical phenomena is called charge. The charge is of two- types positive and negative.
• Law of charge conservation: Charge is neither created nor destroyed; it can only be transferred from one system to another.

EXPLANATION:

• The total charge on the two spheres will be conserved by the law of charge conservation
• But energy may not conserve because if they are of a different size or have different charge then some of their energy might lose in the redistribution of charge.
• In the case of the final potential, it is not always the mean of original potential because during the redistribution of charge some losses occur, but final potential on both spheres is always equal.

• People mistakenly think that an object gets a positive charge by receiving extra positive charges, it losses negative charge (electrons) to become positive.

The correct answer is its radius increases.

• What happens when some charge is placed on a soap bubble its radius increases.

Key Points

• The radius of the bubble will expand because the charged particles uniformly distributed on it causes them to repel each other due to the electrostatic force.
• The phenomenon takes place in both positive and negatively charged bubbles because of the charge on it. 

Additional Information

• Soap bubble exhibits the phenomenon of interference.
• When two light waves from different coherent sources meet together, then the distribution of energy due to one wave is disturbed by the other.
• The modification in the distribution of light energy due to the superposition of two light waves is called "Interference of light".
• The interference principle for light waves was promoted by T. Young.
• Optical interference shows the wave nature of light.

CONCEPT:

Electric Charge

• It is defined as the intrinsic property of certain fundamental particles like electrons, proton, etc, due to which they produce electric and magnetic effects.
• Types of electric charge
  1. ​Positive charge: A body having a deficiency of electrons.
  2. ​Negative charge: A body having an excess of electrons.
• Properties of electric charge
  • Like charges repel and unlike charges attract each other.
  • A charge is a scalar quantity.
  • A charge is always quantized.
  • A charge will always remain conserved.
  • A charge is always associated with mass.
  • The unit of charge is the coulomb.

⇒ 1 coulomb = charge on 625 × 1016 electrons

EXPLANATION:

• ​Positive charge: A body having a deficiency of electrons and the number of protons becomes more than the number of electrons.
• ​Negative charge: A body having an excess of electrons and the number of electrons becomes more than the number of protons.
• Neutron is not responsible for the charge on the element.
• The number of neutrons becomes more than the number of electrons in the element, by this statement, we can't predict whether the number of protons is more than, less than, or equal to the number of electrons in the element.
• So we can't predict the type of charge on the element. Hence, option 4 is correct.

CONCEPT:

• Electric charge: It is an intrinsic property of the elementary particles of matter which gives rise to electric force between various objects.
• It is a scalar quantity.
• SI unit of electric charge is coulomb (C).

EXPLANATION:

• Like charged repel each other. Therefore option 2 is incorrect statement and hence correct answer.

Additional Information

• Conservation of charge is the property by virtue of which total charge of an isolated system always remains constant or conserved. 
• Aditivity of charge is a property by virtue of which total charge of a system is obtained simply by adding algebraically all the charges present anywhere on the system. Thus option 3 is correct.
• Conservation of charge is the property by virtue of which total charge of an isolated system always remains constant or conserved. 
• Quantization of Charge: The charge on any object is the integral multiple of charge of  an electron.

The correct answer is option 1) i.e. 2μC.

CONCEPT:

• Electric charge is a property of particles by which they have a tendency to attract or repel each other without touching. 
  • Electric force: Particles possessing opposite charges attract each other and particles possessing like charges repel each other. This force of attraction or repulsion is called electric force.
• Coulomb's law: The relationship between the electric charges and electric force is given by Coulomb's law.
  • Coulomb's law states that the electrical force between two charged objects is directly proportional to the product of the quantity of charge on the objects and inversely proportional to the square of the distance between the two objects.

The electric force is given as:

 \(F = \frac{kq_1 q_2}{r^2}\)

​Where F is the electric force acting between the two charges, q₁ and q₂ are the two charges, r is the center to center distance between the two objects and k is the proportionality constant known as the Coulomb's law constant and is equal to 9 \(\times \)10⁹ Nm²/C².

CALCULATION:

Given that:

The two charges q₁ and q₂ are identical \(\Rightarrow q_1=q_2=q\)

Electric force (F) of repulsion between the charges = 10 g wt = 10 \(\times \)10^-3 kg \(\times \)10 m/s² = 0.1 N

Distance between the two charges (r) = 0.6 m

\(F = \frac{kq_1 q_2}{r^2}\) \(=\frac{kq^2}{r^2}\)

\(0.1 = \frac{(9 \times 10^9) q^2}{0.6^2}\)

\(q = \sqrt{\frac{0.1 \times 0.6^2}{9\times10^9}}\)\(= 2 \times 10^{-6} C\) = 2 μC

Therefore, the identical charges are 2μC.

Mistake Points

• One kilogram weight (1 kg wt) is the gravitational force acting on a body of mass 1 kg.
• 1 kg wt is converted to newton as follows: 1 kg \(\times\) g = 1 kg \(\times\) 9.81 m/s² = 9.81 N
  • ​Therefore, 1 g wt = 10^-3 kg \(\times\) 9.81 m/s²   (Assuming g = 9.81 m/s²)

CONCEPT:

Electric Charge

• It is defined as the intrinsic property of certain fundamental particles like electrons, proton, etc, due to which they produce electric and magnetic effects.
• Types of electric charge
  1. ​Positive charge: A body having a deficiency of electrons.
  2. ​Negative charge: A body having an excess of electrons.
• Properties of electric charge
  • Like charges repel and unlike charges attract each other.
  • A charge is a scalar quantity.
  • A charge is always quantized.
  • A charge will always remain conserved.
  • A charge is always associated with mass.
  • The unit of charge is the coulomb.

⇒ 1 coulomb= charge on 625×1016 electrons

EXPLANATION:

• ​Positive charge: A body having a deficiency of electrons.
• We know that the proton is present in the nucleus so we can't add or remove protons in the element but we can add or remove electrons from the element.
• So the body can be positively charged by removing electrons and negatively charged by adding electrons.
• A charge cannot be generated by adding or removing protons. Hence, option 2 is correct.

As we know, q = ne,

Where q is the total charge, n is the no of electrons and e is the charge on one electron.

q = 1 mC = 10^-3 C 

e = 1.6 × 10^-19

∴ 10^-3 = n × 1.6 × 10^-19

\( \Rightarrow n = \frac{{{{10}^{ - 3}}}}{{1.6 \times {{10}^{ - 19}}}} = 6.25 \times {10^{15}}\)