Some important questions with answers class 10th science chapter Electricity

 

SOME IMPORTANT QUESTIONS with ANSWERS CLASS 10TH SCIENCE CHAPTER ELECTRICITY

 

Important Questions With Answers ( ELECTRICITY )

 

1.   Define electric current. What is its SI unit? Describe the direction of flow of current in a closed circuit.

Answer: Electric current is the flow of electric charge in a circuit. Its SI unit is Ampere (A). In a closed circuit, the current flows from the positive terminal of the battery or power source to the negative terminal.

2.   State Ohm's law and explain its mathematical equation. How is resistance related to current and voltage?

Answer: Ohm's law states that the current flowing through a conductor is directly proportional to the voltage applied across it, and inversely proportional to the resistance of the conductor.

Ohm's law is expressed as I = V/R,

where I represents the current in Amperes, V represents the voltage in Volts, and R represents the resistance in Ohms. The relationship shows that as the resistance increases, the current decreases for a given voltage, and vice versa.

3.   Define electric potential difference. How is it related to the flow of electric current?

Answer: Electric potential difference, also known as voltage, is the difference in electric potential between two points in an electric circuit. It is denoted by the symbol V and measured in Volts. Electric potential difference creates an electric field that drives the flow of electric charges or current in a circuit. The higher the voltage, the greater the potential for the electric charges to move or flow.

4.   What is the resistance of a conductor? State the factors on which the resistance of a conductor depends.

Answer: Resistance: opposition offered to the flow of electric current. It is denoted by the symbol R and measured in Ohms.

It depends on:

(i)           length of a wire: R  length of wire.

(ii)             Area of cross section of wire (thickness): R  

(iii)        Temperature: R   Temperature.

5.   Explain series and parallel combinations of resistors. Derive the formula for the total resistance in each case.

Answer: In a series combination of resistors, the resistors are connected end-to-end, forming a single path for the current to flow. The total resistance (Rs) in a series combination is the sum of the individual resistances.

Mathematically, Rs = R1 + R2 + R3 + ...,

where R1, R2, R3, etc., represent the individual resistances.

In a parallel combination of resistors, the resistors are connected side-by-side, providing multiple paths for the current to flow. The total resistance (Rp) in a parallel combination can be calculated using the formula:

1/Rp = 1/R1 + 1/R2 + 1/R3 + ...,

where R1, R2, R3, etc., represent the individual resistances.

6.   State the advantages and disadvantages of using a fuse in an electrical circuit. Which type of material is used for making a fuse? Why?

Answer: The advantages of using a fuse in an electrical circuit are that it acts as a safety device to protect against overcurrent or short circuits. When the current exceeds a certain limit, the fuse wire melts, breaking the circuit and preventing damage to other components.

Disadvantages are that fuses need to be replaced after they melt, and they can cause inconvenience if frequent replacements are required.

Fuses are made of materials with low melting points, such as tin, lead, or an alloy of both. These materials melt easily when the current exceeds the rated value, thus interrupting the circuit and protecting the electrical system.

7.   Define electrical power and state its SI unit. Derive an expression for the power consumed in a circuit using Ohm's law.

Answer: Electrical power is the rate at which electric energy is consumed or transformed in an electrical circuit. It is denoted by the symbol P. The SI unit of power is the Watt (W)

The expression for power consumed in a circuit can be derived using Ohm's law.

 P = VI -----------------(1)

we can use Ohm's law

V = IR -----------------(2)

Put  2 in 1 we get,

P = I²R

P = V²/R,

where P represents power, V represents voltage, I represents current, and R represents resistance.

8.   Differentiate between a voltmeter and an ammeter. How are they connected in a circuit to measure voltage and current, respectively?

Answer: Voltmeter: A voltmeter is a device used to measure the voltage difference across two points in an electrical circuit. It is connected in parallel to the component or section of the circuit where the voltage is to be measured. Voltmeters have high resistance to avoid drawing significant current from the circuit and disrupting the voltage being measured.

Ammeter :An ammeter is used to measure the electric current flowing through a particular section of a circuit. It is connected in series with the component or section of the circuit where the current is to be measured. Ammeters have very low resistance to prevent significant voltage drop across them, ensuring accurate current measurement.

 

9.   Explain why a bulb becomes hot when current flows through it.

Answer: When an electric current passes through the filament, it heats up due to its resistance to the flow of electricity. As a result, the filament becomes so hot that it starts to glow and emit light. The bulb becomes hot because the filament reaches a high temperature and transfers heat to its surroundings through radiation and convection.

10.        What are the safety precautions one should take while using electrical appliances at home?

Answer: When using electrical appliances at home, it is important to take the following safety precautions:

             i.        Always plug appliances into grounded outlets and avoid using extension cords for high-powered appliances.

           ii.        Do not overload electrical outlets with too many appliances or devices.

          iii.        Keep electrical cords away from heat sources, water, and sharp objects to prevent damage and potential electrical hazards.

          iv.        Regularly check and replace damaged cords or plugs.

            v.        Turn off and unplug appliances when not in use.

          vi.        Keep electrical appliances away from flammable materials.

         vii.        Do not touch electrical appliances with wet hands.

       viii.        Install smoke detectors and fire extinguishers in your home.

          ix.        If you experience any electrical issues or faults, seek the assistance of a qualified electrician.

 

11.        State the differences between a series and parallel circuit. Provide examples of each.

Answer: Series Circuit: In a series circuit,

a.    The components are connected in a single path, one after the other.

b.    The same current flows through each component.

c.    the total resistance is the sum of individual resistances.

d.    If one component fuse, the entire circuit will be disconnected.

Parallel Circuit: In a parallel circuit,

a.    the components are connected in multiple paths, branching out from the main circuit.

b.    The voltage across each component remains the same,

c.    the total current is the sum of individual currents.

d.    If one component fails, the other components can continue to operate.

 

12.        What is meant by the term "electric circuit"? Draw a simple schematic diagram of an electric circuit.

Answer: An electric circuit is a closed path or loop through which electric current can flow. It consists of various components, such as battery, conducting wires, and loads (resistors, bulbs, motors, etc.). The circuit allows the flow of electric charges from the power source, through the components, and back to the source.

 

13.        Define the term "resistivity." How is it related to the resistance of a conductor?

Answer: Resistivity is a property of a material that quantifies its inherent resistance to the flow of electric current.

It is denoted by the symbol ρ (rho) and

Unit: ohm-meters (Ω·m). Resistivity depends on the nature and composition of the material.

14.        What is the effect of increasing the length and cross-sectional area of a wire on its resistance?

Answer: Increasing the length of a wire directly increases its resistance. This is because a longer wire offers more opposition to the flow of electric current due to the increased distance that the electrons must travel.

On the other hand, increasing the cross-sectional area of a wire decreases its resistance. This is because a thicker wire provides more space for the electrons to flow, reducing the likelihood of collisions with the wire's atoms or molecules and, consequently, lowering the resistance.

15.        How does the resistance of a conductor change with an increase in temperature? Explain.

Answer: In general, the resistance of a conductor increases with an increase in temperature.

This is because as temperature increases, the atoms or molecules within the conductor vibrate more vigorously, causing more frequent collisions with the moving electrons. These collisions impede the flow of electrons, resulting in an increase in resistance.

16.        Define the term "electric power." How is it related to current and voltage? Give its formula and unit.

Answer: Electric power is the rate at which electrical energy is consumed or transformed in a circuit. It is a measure of how quickly electrical work is done or how quickly electrical energy is converted into other forms, such as heat or light.

Formula : P = V I

The SI unit of electric power is the watt (W),

17. How does an electric fuse protect electrical appliances from damage? Explain its working.

Answer: An electric fuse is a safety device used to protect electrical circuits and appliances from excessive current flow. It contains a thin wire or strip of a material that melts when a current above its rated value passes through it. The melting of the fuse element breaks the circuit, stoppage the flow of current and preventing damage to the electrical components.

18.        Define the term "potential difference." How is it related to the work done in moving a charge?

Answer: Potential difference, work done per unit charge in moving a charge from one point to another within an electric field.

The work done in moving a charge (Q) between two points with a potential difference (V) is given by the equation: work = Q × V

In other words, the potential difference determines the amount of work that can be done by electrical charges in a circuit. It is measured in volts (V).

19.        Define    1 Volt   ,    1 ohm,     1 Coloumb    ,      1 Ampere.

(i)           1 Volt: When one joule of work is done to move a charge of one coulomb from one point to another then voltage is called 1 volt.

(ii)          1 Ohm: When wire is having a potential difference of 1 volt through which 1 ampere is passing.

(iii)        1 Coulomb: When one ampere of current flows through a wire for one second then charge is said to be one coulomb.

(iv)         1 Ampere: When one coulomb of charge flows through any conductor for one second then current is said to be one ampere.

20.        Define Ohm’s Law. Also draw the graph for the Ohm’s Law.

Ohm’s Law: It states that current passing through a conductor is directly proportional to the potential difference across its ends, provides the temperature remains constant.

 

21.        What do you mean by resistance? Write down the factors on which the

 resistance of the circuit depends.

Resistance: Hindrance produced to the flow of electric current. It depends on:

(iv)         length of a wire: R  length of wire.

(v)             Area of cross section of wire (thickness): R  

(vi)         Temperature: R   Temperature.

 

22.        Drive Series and parallel relation for Resistance.

23.        Write down Joule’s Law of heating?

The effect of electric current due to which heat is produced in a wire when current is passed through it is called Joule’s law of heating.

According to this, H is directly proportion to I² RT

24.        When will be the value of resistance be maximum and minimum?

Maximum  in series connection and Minimum in parallel connection.