Advertisements
Advertisements
प्रश्न
The coercive force for a certain permanent magnet is 4.0 × 104 A m−1. This magnet is placed inside a long solenoid of 40 turns/cm and a current is passed in the solenoid to demagnetise it completely. Find the current.
Advertisements
उत्तर
Given:-
Number of turns per unit length, n = 40 turns/cm = 4000 turns/m
Magnetising field, H = 4 × 104 A/m
Magnetic field inside a solenoid (B) is given by,
B = µ0nI,
where, n = number of turns per unit length.
I = current through the solenoid.
\[\therefore \frac{B}{\mu_0} = nI = H\]
\[\Rightarrow H = \frac{N}{l}I\]
\[ \Rightarrow I = \frac{Hl}{N} = \frac{H}{n}\]
\[ \Rightarrow I = \frac{4 \times {10}^4}{4000} = 10 A\]
APPEARS IN
संबंधित प्रश्न
What are permanent magnets? Give one example ?
Why is the core of an electromagnet made of ferromagnetic materials?
The force on a north pole, `vecF = mvecB` , parallel to the field `vecB` . Does it contradict our earlier knowledge that a magnetic field can exert forces only perpendicular to itself?
A tangent galvanometer is connected directly to an ideal battery. If the number of turns in the coil is doubled the deflection will
Consider the situation of the previous problem. The directions of the magnetic field due to the dipole are opposite at
(a) P1 and P2
(b) Q1 and Q2
(c) P1 and Q1
(d) P2 and Q2
Figure shows some of the equipotential surfaces of the magnetic scalar potential. Find the magnetic field B at a point in the region.
The magnetic field at a point, 10 cm away from a magnetic dipole, is found to be `2.0 xx 10^-4 "T"` . Find the magnetic moment of the dipole if the point is (a) in end-on position of the dipole and (b) in broadside-on position of the dipole.
A magnetic dipole of magnetic moment `1.44 "A m"^2`is placed horizontally with the north pole pointing towards north. Find the position of the neutral point if the horizontal component of the earth's magnetic field is 18 μT.
Do permeability and relative permeability have the same dimensions?
Why is it not possible to make permanent magnets from paramagnetic materials?
The desirable properties for making permanent magnets are _________________ .
If the earth's magnetic field has a magnitude 3.4 × 10−5 T at the magnetic equator of the earth, what would be its value at the earth's geomagnetic poles?
The needle of a dip circle shows an apparent dip of 45° in a particular position and 53° when the circle is rotated through 90°. Find the true dip.
A short magnet oscillates in an oscillation magnetometer with a time period of 0.10 s where the earth's horizontal magnetic field is 24 μT. A downward current of 18 A is established in a vertical wire placed 20 cm east of the magnet. Find the new time period.
A bar magnet makes 40 oscillations per minute in an oscillation magnetometer. An identical magnet is demagnetized completely and is placed over the magnet in the magnetometer. Find the time taken for 40 oscillations by this combination. Neglect any induced magnetism.
What should be retentivity and coercivity of permanent magnet?
In a permanent magnet at room temperature ______.
Assertion: Electromagnetic are made of soft iron.
Reason: Coercivity of soft iron is small.
Which magnetic properties are desirable for making a permanent magnet?
