Long Answer – Class 10 -Science-Physics-Chapter13: Magnetic Effects Of Electric Current

Class 10 -Science-LongAnswer – Physics-Chapter13: Magnetic Effects Of Electric Current

Q1. (a) Write the values of the following physical quantities in connection with domestic power supply in our country:

 (i) potential difference between live wire and neutral wire.

(ii) frequency of ac.

(b) Explain the role of the following as safety measure in domestic electric appliance/circuits: (i) earth wire (ii) fuse.

Ans : (a) (i) 220 V, (ii) 50 Hz

(b) Safety measure in electric appliance/circuits:

(i) Earth wire is a safety device to protect us from electric shock due to leakage of current or faulty  electric appliances. An earth wire is a thick copper wire connected to a metal plate buried deep in the earth. The metallic body of the electric appliance is connected to the earth wire, it provides a low resistance conducting path and leaked current goes to deep in the earth and human beings do not get a fatal electric shock.

(ii) Fuse: It is also a safety device. It is a wire of an alloy with low melting point. If a current greater than a particular values flows in the circuit it will melt and circuit is broken and stops power supply in the circuit.

Q2. The given figure shows a domestic electric circuit. Study this circuit carefully. List any two errors in the circuit and justify your answer.

(b) Give one difference between the wires used in the element of an electric heater and in a fuse.

(c) List two advantages of parallel connection over series connection.

Ans : 

(a) Errors in the circuit

(i) Fuse wire is connected in neutral wire (N) where as it must be connected in live wire (L).

(ii) Circuit of bulb B2 is incomplete.

(b) Element of electric heater has high resistance and high melting point whereas a fuse wire has high resistance and low melting point.

(c) Advantages of parallel connection over series connection.

(i) In parallel combination if one appliance fails to work others keep working.

(ii) Potential difference across each appliance remains same.

Q3.  (a) Define electromagnetic induction.

(b) Two coils P and S are wound over the same iron core. Coil P is connected to battery and key the coil S is connected to galvanometer. Draw a suitable diagram of this arrangement and write your observations when:

(i) current in the coil P is started by closing the key.

(ii) current continues to flow in coil P.

(iii) current in coil P is stopped by removing the key. Explain the reason for such observations.

Ans : a. The phenomenon by producing a current in a coil by changing magnetic field associated with it or by changing a current in the neighbouring coil is called electromagnetic induction. Current so produced is called induced current.

(i) When key K is closed due to increasing current a magnetic field is produced which is changing. In this changing magnetic field coils is kept so an induced current flow through it, so galvanometer shows a deflection.

(ii) After some time current reaches maximum and becomes constant in P coil. There is no change in current so there is no change in magnetic field associated with coil S and hence no induced current in coil S. Deflection in galvanometer becomes zero.

(iii) Current becomes zero from maximum in coil P and hence galvanometer shows a deflection but now it is in opposite direction.

Q4. Answer the following questions:

a. What is the direction of magnetic field lines outside a bar-magnet?

b. Why two magnetic field lines cannot intersect each other?

c. What is indicated by crowding of magnetic field lines in a given region?

d. What is the frequency of ac in India?

 e. State one advantage of ac over dc.

Ans :a. From N pole to S pole

b. If two magnetic field lines would intersect each other then at the point of intersection there would be two different directions of magnetic field which is not possible.

c. Magnetic field strength is more in that region.

d. 50 cycles per sec (c/s) or Hz.

e. AC can be step up for transmission over a longer distances with less power loss.