Download 7TH CLASSES PHYSICS DAILY PLAN

10th CLASSES
PHYSICS
DAILY PLAN
8) Magnetic force between two current-carrying wires:
SUBJECT: Force on current carrying conductor and
B1
I1
charged particle
AIM: to determine force on a current carrying
conductor and torque on a current carrying loop
DURATION: 160min
REAL LIFE: galvanometer,el.motor.
PRESENTATION:
F
d
F
B2
I2
L
[Parallel currents having the same direction attract each other]
I
B
B
I=0
B
B1
I2
B2
F
I
Right hand rule-2:
B :: Fingers
I :: Thumb
F :: Inside the hand
F
[Parallel currents having opposite directions repel each other]
[Note: F = F even if the currents are different. This is because of the
third law]
Magnitude of force:
Formula:
F=I1 L B2
μ I
μ I I
F= I1 L ( 0 2 ) F = 0 1 2 L
2π d
2π d
I
L
I1
F=I L B
B
F
μ I I
F
= 0 1 2
L
2 d
or
Ex: Find net force on the loop.
Ex:
Find net force on I3.
I2
General formula:
I
I1
I1
I2 I3
L
L
F
L
B
L
d
x
x

L
9) Torque on current loop:
F=I L B
F = I (L Sin) B
Note:  is between B and I.
Class activity: Hold two pens ends
together in different orientations and
show that they always determine a
plane unless they are parallel. Place a
third pen perpendicular to them as
the force vector.
Ex:
..F = I L B Sin
F
F
I
S
N

I
B
F
B
I=5A
Torque= 2 F a
2a
2Wb/m2
10 cm
 = 2 (I L B) a
 = I B (2aL)
Find F=?
I
I
F
F
127°
1.2 T
Ex: What is the force on the
wire?
(Sin 45°=0.707)
L
 =
I B (Area).
4A
20 cm
45°
Side view:
F
a
I
a
I
F
 = 2 F a
y

Ex: Find direction of F or B
B
a
a

F
I
B
v
+
a Sin
v
B
+
 = 2 F a
 = 2 F a Sin
I
F
F
v
Trajectory of particle: Since F is always perpendicular to v,
the charge will perform circular motionwith constant speed.
 = I B (Area) Sin
( is between B and Normal)
[So torque is zero when normal is parallel to B]
Applications:
A) Galvanometer:
Used to measure small currents
v
B
+
v
F
+
F
F
N
S
I
I
spring
B) Electric motor:
Class activity: Showing a real electric motor and describing
how current changes direction when torque becomes zero.
10) Force acting on a charge moving in magnetic field:
[Force on current is sum of magnetic forces on moving
charges in the wire]
F
F
v
+
F
F
+
v
F
v
+
+
v
[Magnitude of this force is proportional to magnitudes of charge,
magnetic field and velocity]
q
Right hand rule for (+) charge:
(Hand stretched)
B
+
+
r=
Fc = m ac
v
mv
qB
q v B = m v2 / r
Ex: Electrons having 107 m/s velocity are shot into magnetic
field of 8 x 10-4 T. Find radius of trajectory.
(me = 9 x 10-31kg, e = 1.6 x 10-19 C)
Ex:
a) Determine
of charges.
b) Find q1/q2=?
masses of
particles are
sign
q2 if
2
v
When a charge moves in magnetic filed, cutting the field lines,
there is a magnetic force on the charge.
F
r
v
+
v
+
Finding radius:
Voltmeters and ampermeters are produced by connecting a
galvanometer with a resistance in series or parallel.
B
+
r
F
v
B
q1 v
equal.
B
Ex:
q
+
m
B
2v
m
+
Compare the period of
revolution for two
identical particles.
q
v
v
q
B ::: Fingers
v ::: Thumb
F ::: Inside the hand
v
Sol: Periods are equal:
F
+
Magnitude of force:
2v
B
F = q v B
2r
+
v
r
General formula:
B

q +
F = q v B
v
v
F = q (v Sin) B
v
F = q v B Sin
 is between B and v...
F
Rule: There can be any angle
between v and B. But F is always
perpendicular to both v and B.

v
HOMEWORK: 23-24-26-27-28-34-35
MULTIMEDIA: Basic 48,Cerway 3,Akademedia
DEMONSTRATION: mag.force on a cond.
EXPERIMENT:
TEACHER:
DIRECTOR:
B