Advertisements
Advertisements
प्रश्न
A cylindrical bar magnet is rotated about its axis (Figure). A wire is connected from the axis and is made to touch the cylindrical surface through a contact. Then
पर्याय
a direct current flows in the ammeter A.
no current flows through the ammeter A.
an alternating sinusoidal current flows through the ammeter A with a time period T = 2π/ω.
a time varying non-sinosoidal current flows through the ammeter A.
Advertisements
उत्तर
A cylindrical bar magnet is rotated about its axis (Figure). A wire is connected from the axis and is made to touch the cylindrical surface through a contact. Then no current flows through the ammeter A.
Explanation:
The phenomenon of electromagnetic induction is used in this problem. Whenever the number of magnetic lines of force (magnetic flux) passing through a circuit changes (or a moving conductor cuts the magnetic flux) an emf is produced in the circuit (or emf induces across the ends of the conductor) is called induced emf. The induced emf persists only as long as there is a change or cutting of flux.
When cylindrical bar magnet is rotated about its axis, no change in flux linked with the circuit takes place, consequently no emf is induced and hence, no current flows through the ammeter A. Hence the ammeter shows no deflection.
APPEARS IN
संबंधित प्रश्न
A square loop MNOP of side 20 cm is placed horizontally in a uniform magnetic field acting vertically downwards as shown in the figure. The loop is pulled with a constant velocity of 20 cm s−1 till it goes out of the field.
(i) Depict the direction of the induced current in the loop as it goes out of the field. For how long would the current in the loop persist?
(ii) Plot a graph showing the variation of magnetic flux and induced emf as a function of time.
Draw a schematic sketch of an ac generator describing its basic elements. State briefly its working principle. Show a plot of variation of
(i) Magnetic flux and
(ii) Alternating emf versus time generated by a loop of wire rotating in a magnetic field.
A pair of adjacent coils has a mutual inductance of 1.5 H. If the current in one coil changes from 0 to 20 A in 0.5 s, what is the change of flux linkage with the other coil?
How does the mutual inductance of a pair of coils change when
(i) distance between the coils is increased and
(ii) number of turns in the coils is increased?
A metallic loop is placed in a nonuniform magnetic field. Will an emf be induced in the loop?
An inductor is connected to a battery through a switch. Explain why the emf induced in the inductor is much larger when the switch is opened as compared to the emf induced when the switch is closed.
Calculate magnetic flux density of the magnetic field at the centre of a circular coil of 50 turns, having a radius of 0.5m and carrying a current of 5 A.
Find magnetic flux density at a point on the axis of a long solenoid having 5000 tums/m when it carrying a current of 2 A.
Whenever the magnetic flux linked with an electric circuit changes, an emf is induced in the circuit. This is called ______.
Two inductors of inductance L each are connected in series with the opposite? magnetic fluxes. The resultant inductance is ______.
The magnetic flux linked with the coil (in Weber) is given by the equation- Փ = 5t2 + 3t + 16. The induced EMF in the coil at time, t = 4 will be ______.
The dimensions of magnetic flux are ______
The unit of magnetic flux in SI is ______
A coil is placed in a time varying magnetic field. If the number of turns in the coil were to be halved and the radius of wire doubled, the electrical power dissipated due to the current induced in the coil would be: (Assume the coil to be short circuited.)
A circular coil of 1000 turns each with area 1 m2 is rotated about its vertical diameter at the rate of one revolution per second in a uniform horizontal magnetic field of 0.07T. The maximum voltage generation will be ______ V.
A circular coil has radius ‘r', number of turns ‘N’ and carries a current ‘I’. Magnetic flux density ‘B’ at its centre is ______.
