Advertisements
Advertisements
Question
To measure the magnetic moment of a bar magnet, one may use
(a) a tangent galvanometer
(b) a deflection galvanometer if the earth's horizontal field is known
(c) an oscillation magnetometer if the earth's horizontal field is known
(d) both deflection and oscillation magnetometer if the earth's horizontal field is not known
Advertisements
Solution
(b) a deflection galvanometer if the earth's horizontal field is known
(c) an oscillation magnetometer if the earth's horizontal field is known
(d) both deflection and oscillation magnetometers if the earth's horizontal field is not known
Denial of (a):
Tangent galvanometer is an instrument used to measure electric current; it cannot be used to the measure magnetic moment of a bar magnet.
Justification of (b) and (c) :
Deflection magnetometer is used to measure `M/B_H` of a permanent bar magnet.
Similarly, oscillation magnetometer is used to measure `MB_H` of a bar magnet. So, if earth's horizontal field, `B_H` is known, then the magnetic moment of a bar magnet, M, can be measured.
Justification of (d):
Using deflection and oscillation magnetometers, we can calculate `M/B_H` and `MB_H` respectively . Therefore, if we multiply the result obtained from both the instruments, then BH cancels out as `M/B_H xx MB_H = M^2` . Thus, the value of `B_H` is not required.
Therefore, we can use both deflection and oscillation magnetometers if the earth's horizontal field is not known.
APPEARS IN
RELATED QUESTIONS
State any two advantages of electromagnets over permanent magnets.
State two advantages of an electromagnet over a permanent magnet.
Can we have a single north pole, or a single south pole?
Compare the direction of the magnetic field inside a solenoid with that of the field there if the solenoid is replaced by its equivalent combination of north pole and south pole.
Magnetic scalar potential is defined as `U(vec r_2) - U(vec r_1) = - ∫_vec(r_1)^vec(r_2)` `vec (B) . dvec(l)`
Apply this equation to a closed curve enclosing a long straight wire. The RHS of the above equation is then `-u_0 i` by Ampere's law. We see that `U(vec(r_2)) ≠ U(vec(r_1))` even when `vec r_2 =vec r_1` .Can we have a magnetic scalar potential in this case?
Which of the following four graphs may best represent the current-deflection relation in a tangent galvanometer?
A very long bar magnet is placed with its north pole coinciding with the centre of a circular loop carrying as electric current i. The magnetic field due to the magnet at a point on the periphery of the wire is B. The radius of the loop is a. The force on the wire is
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.
Show that the magnetic field at a point due to a magnetic dipole is perpendicular to the magnetic axis if the line joining the point with the centre of the dipole makes an angle of `tan^-1(sqrt 2)` with the magnetic axis
Do permeability and relative permeability have the same dimensions?
A short magnet produces a deflection of 37° in a deflection magnetometer in Tan-A position when placed at a separation of 10 cm from the needle. Find the ratio of the magnetic moment of the magnet to the earth's horizontal magnetic field.
The combination of two bar magnets makes 10 oscillations per second in an oscillation magnetometer when like poles are tied together and 2 oscillations per second when unlike poles are tied together. Find the ratio of the magnetic moments of the magnets. Neglect any induced magnetism.
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.
Which property of soft iron makes it useful for preparing electromagnet?
Answer in brief.
Explain one application of electromagnet.
In a permanent magnet at room temperature ______.
