Moving charges and magnetism Flashcards
The magnetic effect of electric current was discovered by :
Oersted
A moving charge produces
Both electric and magnetic field
The SI unit of magnetic field intensity is
N / A-m
The magnetic field produced at the centre of a circular coil carrying current is :
Perpendicular to the plane of coil
The force on a charge moving in a uniform magnetic field is zero if the direction of motion of charge is :
parallel to the magnetic field
In _____ device a high resistance is joined in series with the coil of galvanometer
Voltmeter
A charged particle enters in a unifrom magnetic field parallel to field, the path of particle will be :
Straight line
The SI unite of permeability and magnetic field is :
i) newton / ampere^2
ii) newton / (ampere x metre )
Dimensional formula of magnetic field is :
M T^ -2 A ^ -1
A current carrying solenoid behaves like a :
Bar magnet
The lorence force on a charged particle in a uniform magnetic field is known as
q ( v x b)
;v & b are vectors
The force between two parallel conductors carrying current in same direction is _______ in nature.
Attractive
The resistance of an ideal voltmeter is _______
Infinite
In an electric circuit, voltmeter is always joined in ________
parallel
The resistance of an ideal ammeter is
Zero
The force acting on a moving charge in a magnetic field is called
Lorentz force
Magnetic field is a _____ quantity
Vector
The ______ of the galvanometer is reduced by the use of shunt
Sensitivity
What is the magnetic field at the centre of a current carrying pipe of copper
Zero
What is the relation between radius of a current carrying coil and magnetic field produced at its centre
B is inversely proportional to R
A charged particle enters in a uniform magnetic field parallel to field. What will be its path ?
The path of charged particle will be a straight line
How is galvanometer converted into a voltmeter
To convert a galvanometer into voltmeter, a high resistance wire is joined in series with coil of galvanometer
When will two parallel current carrying condecutors :
i) attract each other
ii) repel each other
i) when the current flows through parallel wires in same direction
ii) when the current flows through parallel wires in opposite direction
SIGN CONVENTION OF CURRENT IN A FIELD
A current or a
field (electric or magnetic) emerging out of the plane of the paper is depicted by a dot (⨀). A current or a field going
into the plane of the paper is depicted by a cross (⨂ )
FORCE DUE E AND B
F = q [ E (r) + v × B (r)] º F electric +F magnetic
The magnetic force is zero if charge is not moving (as then |v|= 0). Only a moving
charge feels the magnetic force.
true
formula of b
[B] = [F/qv]
Magnetic force on a current-carrying conductor
F = (nlA)q vd
´ B
MOTION IN A MAGNETIC FIELD
The particle will describe a circle if v and B are perpendicular to each other
motion in a plane
perpendicular to B is as before a circular one, thereby producing a helical motion
ANGLUAR FREQUWNCY of helical path
w = 2pi v = q B/ m
time period of helical path
p = v||T = 2pm v||/ q B
MAGNETIC FIELD DUE TO A CURRENT ELEMENT,
BIOT-SAVART LAW
=µ0 I dl r/
4π r^3
µ0/4π=
10^-7 Tm/A
DIFFERANCE BETWEEN E AND B
(i) Both are long range, since both depend inversely on the square of distance from the source to the point of interest. The principle of superposition applies to both fields. [In this connection, note that the magnetic field is linear in the source I dl just as the electrostatic field is linear in its source: the electric charge.]
(ii) The electrostatic field is produced by a scalar source, namely, the electric charge. The magnetic field is produced by a vector source I dl.
(iii) The electrostatic field is along the displacement vector joining the source and the field point. The magnetic field is perpendicular to the plane containing the displacement vector rand the current element I dl.
(iv) There is an angle dependence in the Biot-Savart law which is not present in the electrostatic case. Along this line,q = 0, sin q = 0 and from|dB| = 0.
ε0 µ0=
1/c^2
MAGNETIC FIELD ON THE AXIS OF A CIRCULAR
CURRENT LOOP
dB= µ0 I dl / 4 pi [x^2+R^2]
WRITE RIGHT HAND THUMB LAW
Curl the palm of your right hand around the circular wire with the fingers pointing in the direction of the current. The right-hand thumb gives the direction of the magnetic field.
AMPERE’S CIRCUITAL LAW
∮B.dl = µ0I
MAGNETIC FIELD IN A LONG SOLENOID
B = µ0n I
Parallel currents attract, and antiparallel currents repel
TRUE
force b/w 2 parallel current carrying wire
fab = µ0 Ia Ib/ 2 pi d
Torque on a rectangular current loop in a uniform
magnetic field
ɽ= I A B
A= area
B= magnetic field
magnetic moment of the current loop
m = I A
Circular current loop as a magnetic dipole
refer ncert
study moving coil galvonometer
