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Conceptual questions on magnetic effects of current for Class 10 physics



Question 1) 
Arun while studying the force experienced by a current carrying conductor in a magnetic Field records the following observation
1
The force experienced by the conductor is increases as the current in the conductor is decreased
2
The force experienced by the conductor is decreases as the strength of magnetic field  is decreased
3
Direction of the force on the current carrying conductor is determined suing Fleming Left hand rule
Which of these observations is correct? Explain
Solution)   F=iLB
a) So as current is decreased, Force also decreases. Observation is Incorrect
b) Again, Force experience is decreased as strength of magnetic field is decreased. Observation is correct
c) Observation is correct
Question 2)
Write down the difference between permanent magnet and Electromagnet?
Solution)
S.no
Permanent Magnet
Electromagnet
1
Those magnets which have permanent magnetic field around it are called permanent Magnet
When a soft core is placed inside a solenoid and current is passed through it, the soft iron gets magnetized. The magnet so formed are called electromagnet
2
Permanent magnets are important for their industrial uses especially when it comes to power generation and electric motors. The induction process for turbines and generators needs permanent magnets to turn mechanical motion into energy. They are also important for electric motors in many electronics using the reverse of the induction of electric current to make mechanical energy. As you can see without the permanent magnet we would not be able to take full advantage of the capabilities of electricity in modern devices.
As soon as the current is stopped, the soft iron becomes demagnetized.
They are used in cranes, electric bell etc.
Question 3
 Why two magnetic field lines cannot intersect with each other?
Solution)
if two magnetic field lines intersect with each other, then there will be two tangents drawn  which gives direction of magnetic field at the point of intersection. This is not possible
Question 4)
 A coil of insulated copper wire is connected to a galvanometer. What happens if a bar magnet is
1
Pushed into the coil
2
Withdrawn from inside the coil
3
Held stationary inside the coil
What is the name of the phenomenon?
Solution)
1
Pushed into the coil
An induced current is produced due to electromagnetic induction. Galvanometer will show deflection
2
Withdrawn from inside the coil
An induced current is produced due to electromagnetic induction. Galvanometer will show deflection in opposite direction
3
Held stationary inside the coil
No deflection
Phenomenon is electromagnetic Induction
Question 5) 
Answer these short questions regarding Magnetic field?
a) What does crowding of magnetic lines indicate?
b) SI unit of Magnetic field?
c) What is the direction of magnetic field lines outside a bar magnet?
Solution)
S.no
Question
Answer
1
What does crowding of magnetic lines indicate?
Strength of Magnetic field
2
SI unit of Magnetic field?
Oersted
3
What is the direction of magnetic field lines outside a bar magnet?
North Pole to South Pole
Question 6
 What is difference between Direct Current DC and Alternating Current?
Which one is used to transmit long power over long distances?
What is the frequency of the Power transmission in India?
Solution) 
a) The difference are noted down below
S.no
Direct Current
Alternating current
1
Magnitude of current remains constant.
It flows in one direction in the circuit.
It changes continuously
It reverses its direction while flowing in a circuit
2

 

3
Battery provides direct current
AC  generator provides AC current
4
The frequency of alternating current is 50Hz or 60Hz depending upon the country.
The frequency of direct current is zero.
b) AC is used to transmit long power as loss of energy in transmission is comparatively small
c) 50Hz is the frequency of transmission of current in India
Question 7)
 Why do we use fuse in series with any electrical appliance? Why should a fuse with defined rating not be replaced by one with larger rating?
Solution)
 Fuse is used for protecting appliances due to short circuit or overloading. The fuse is rated for a certain maximum current and blows off when a current more than rated value flows through it
If a fuse is replaced by one with large ratings, the appliances may get damaged while the protecting fuse does not burn off.
Question 8)
 True and False Statements
A) North poles repel North poles
B) South poles repel south poles
C) North poles attract south poles
D) South poles attract north poles
E) The force of attraction or repulsion varies directly proportional with the distance squared
F) The strength of a magnet varies at different locations on the magnet
G) Magnets are Weakest at their poles
H) The horse-shoe shape is very commonly used in magnetic separators because its lines of force are mostly at the open end of the horse-shoe, and this helps in the separation of ferrous materials. I) Magnetic field lines are closed loops.  They enter a magnet at its South Pole, and exit a magnet at its North Pole.
Solutions
A) True
B) True
C) True
D) True
E) False, it is inversely proportional
F) True
G) False, Magnets are strongest at the Poles
H) True
I) True
Question 9) 
Write Difference between Electric and Magnetic Field
Solutions
Electric Field
Magnetic Field
It is created around electric charge
It is created around moving electric charge and magnets
The unit of electric Field is Newton per coulomb, ,volts per meter
The unit of magnetic Field is Gauss or Tesla
Force in Electric field is proportional to the electric charge
Force in magnetic Field is proportional to charge and speed of electric charge

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