# Class 10th Physics unit 14 Question An Anwer

## Class 10th Physics unit 14 Question An Anwer On Newsongoogle By Bilal Articles

Explore comprehensive answers to Class 10th Physics Unit 14 questions on Newsongoogle by Bilal Articles. Enhance your understanding with detailed explanations and insights to excel in your studies.

### Unit 14

Q 1. Define electric current.

Ans: The rate of flow of electric charge through any cross-sectional area is called, electric current. lf the charge Q is passing through an area A in time ‘t’ second, then the current.

Q 2. What is meant by the conventional current?

Ans: A current produced due to flow of negative charge is equivalent to a current due to the flow of an equal amount of positive charge in the opposite direction. This equivalent current of positive charge is known as conventional current.

Q 3. Which type of charge is responsible for the flow of current in metallic conductors?

Ans: In metals or metallic conductors, the current is due to the flow of free electrons i.e. negative charges. For example, in a copper wire, there are a large number of free electrons which are in random motion. When we apply a potential difference across the wire, these free electrons move through the wire.

Q 4. In electrolyte which charge is responsible for the flow of current?

Ans: The molecules of electrolytes are dissolved among positive and negative ions in a solution. Thus current in electrolytes is due to the flow of both positive and negative charges.

Q 5. How energy is obtained due to the flow of charges?

Ans: When a positive charge moves from a point of higher potential to a point of lower potential, it gains energy from the electric field. During the flow of electric current, positive charges flow continuously from a high potential to a low potential point. Thus the electric current becomes a continuous source of energy.

Q 6. How a galvanometer is converted into a voltmeter?

Ans: The galvanometer is converted into a voltmeter by connecting suitable resistance in series with it. The value of the resistance depends upon the range of the voltmeter. Usually, its value is several thousand ohms. Thus the resistance of a voltmeter is very high.

Q 7. How a galvanometer is converted into an ammeter?

Ans: A Galvanometer can be converted into an ammeter by connecting a small resistance parallel to it. This small resistance is known as a “shunt”. Shunt provides an alternative path for the current to flow. The major part of the current passes through the shunt and a small fraction of it flows through the galvanometer.

Q 8. Why resistance of the ammeter is kept low?

Ans: lf the resistance of the ammeter is kept high, then a high amount of current flows through the galvanometer. When a high amount of current flows through the galvanometer then the galvanometer can be burnt. that is why the resistance of the ammeter is kept low.

Q 9. Why resistance of the voltmeter is kept high?

Ans: If the resistance of the voltmeter is comparatively low, it will draw more current from the circuit. Due to this the potential difference across the resistance for the measurement, of which the voltmeter was connected, would drop.

Q 10. On what factors reliability of the voltmeter depend?

Ans: Higher the resistance of the voltmeter. More reliable would be its readings. Therefore, a good voltmeter should have such a high resistance so that no or very little current could pass through it.

Q 11. Differentiate between electromotive force and potential difference.

Ans: Electromotive force: the electromotive force of a battery or cell is the total energy supplied in driving a one-coulomb charge around a complete circuit in which the cell is connected. The complete circuit includes the cell and external circuit connected to the terminals. Potential difference: the potential difference determines the energy between any two points of the circuit which is required in moving a charge from one point to another.

Q 12. State and explain Ohm’s law. Write down its limitations.

Ans: “The value of current I passing through a conductor is directly proportional to the potential difference V applied across its ends, provided the temperature and the physical state of the conductor do not change. Mathematical form: V = IR Limitations of Ohm’s law: Ohm’s Law is applicable only in the case of metallic conductors when their temperature and physical state do not change.

Q 13. Define resistance and its unit.

Ans: The property of a substance that opposes the flow of current through it is called its resistance. Where R is resistance, V is the potential difference and I is current., S.I unit of resistance is Ohm. Which is defined as Ohm: “lf a current of one ampere passes through it when a potential difference of one volt is applied across its ends then resistance would be one Ohm. Ohm is usually represented by the Greek letter Ω.

Q 14. What are the factors upon which the resistance of a conductor depends?

Ans: Resistance of the conductor depends upon the following factors: i. Length of the conductor (L) ii. Area of cross-section of the conductor (A) iii. Nature of the conductor iv. Temperature

Q 15. Why does the resistance of a conductor increase with the rise of its temperature?

Ans: When the temperature of the conductor rises, the average speed of the random motion of the free electrons increases, which enhances the rate of collision of electrons and atoms. This causes an increase in the resistance of the conductor.

Q 16. Why do we always use metal wires for the conduction of electricity?

Ans: Because they are good conductors of electricity and offer less resistance to the flow of current. Metals like silver and copper have an excess of free electrons which are not held strongly with any particular atom of metals. These free electrons move randomly in all directions inside metals. When we apply an external electric field these elections can easily move in a specific direction. This movement of free elections in a particular direction under the influence of an external field causes the flow of current in metal wires.

Q 17. What do you mean by insulators?

Ans: The substances through which almost no current flows are called insulators. Bns: Examples: The examples of insulators are glass, wood, plastic, Our, silk, etc.

Q 18. State Joule’s Law.

Ans: The amount of heat generated in a resistance due to the flow of charges is equal to the product of the square of current I, resistance R, and the time duration t. mathematically:

Q 22. What are live and neutral wires?

Ans: Electricity is distributed to various houses in a city from a power station using two wires: i. Neutral wire: One wire is earthed at the power station, so it is at zero potential. This wire is called a neutral wire. This wire provides the return path of the current. It is black or blue. ii. Live wire: The other wire on the power station is at some certain potential called the live wire. The potential difference between both wires is 220. It is red or brown.

Q 23. How electricity is dangerous for us?

Ans: Our body is a good conductor of electricity through which current can easily pass. Therefore, if a person holds the live wire, then because of the presence of voltage in it, current will start flowing to the ground through the human body which may prove fatal for the person.

Q 24. What is cable? And how it should be used?

Ans: “An insulated covered wire is known as cable”. The cable should be used keeping the following things in mind:  The layer of insulation in the cable is perfect and is not damaged.  Sometimes a heavy current flows through the wire and it gets so hot that its insulation is burnt out and the wire becomes naked and it becomes dangerous.  Constant friction also removes the insulation from the wire whereas too much moisture also damages the insulation. In such a situation it is advisable to use a cable with two layers of insulation.

Q 25. Define fuse and write down its principle.

Ans: “A small wire connected ln series with the live wire is known as fuse wire or fuse”. Principle: A specified amount of current can safely pass through it. When the current following through it exceeds this limit, it gets so hot that it melts.

Q 26. What do you know about the Fuse rating?

Ans: We can determine the required fuse rating for a circuit. Suppose we want to insert a fuse for an air conditioner or heater of power 3000W. If the voltage supply is 240V, then according to relation P =V x I, we gel I = 12.5A. The available fuses in the market are usually of rating 5A, 10A, 13A, 30A, etc. Hence suitable fuse for this circuit would be of l3A.

Q 27. What is a Circuit Breaker? Also, write down its principles.

Ans: It is a safety device that is used in place of a fuse. Due to any fault when the current exceeds the safety limit, then the button of the circuit breaker moves upward. Due to this the circuit breaks and the flow of the current is stopped in lt. Principle: The Current flowing through the electric circuit also flows through the coil of the circuit Breaker due to which the coil becomes electromagnet. When the current is within its limits the contact points of the circuit are connected and the circuit is completed. As soon as the current exceeds the limit, the magnetic force of the electromagnet is so increased that it attracts the iron strip towards it. Hence the contact points are separated and the circuit breaks.

Q 28. What is the working principle of Earth wire?

Ans: Whenever the metal casing of the appliance, due to faulty insulation, gets connected with the live wire, the circuit shorts and a large current would immediately flow to the ground through the earth wire and cause the fuse wire to melt or the circuit breaker breaks the circuit. Therefore, the person who is using the appliance is saved.

Q 29. On what principle circuit breaker work?

Ans: The circuit flowing through the electric circuit also flows through the coil of the circuit breaker due to which the coil becomes electromagnet. When the current is within its limits, the contact points of the circuit are connected and the circuit is completed. As soon as the current exceeds the limit, the magnetic force of the electrometric is so increased that it attracts the iron strip towards it. Hence the contact points are separated and the circuit breaks.

Q 30. How earth wire is useful to us?

Ans: Whenever the metal casing of the appliance, due to faulty insulation, gets connected with the live wire, the circuit shorts and a large current would immediately flow to the ground through the earth wire and cause the fuse wire to melt or the circuit breaker breaks the circuit. Therefore, the person who is using the appliance is saved.

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