Magnetic force on currents

N

S

IF

N

S

I

F

P.62

Fleming’sleft-hand rule

P.62

Magnetic field becomesstronger on the top

Magnetic field becomessmaller at the bottom

Neutral point

P.62

To have greater induced magnetic force:

P.62

Increase current

Stronger magnetic field

P.63

NS

NS

I

P.63

Conducting wire with a permanent magnet

N

S

IF

N

S

I

F

P.63

I

I

I

I

x x x x

xxxxx

x

x x x x

xxxxx

x

.

.

.

.

.

.

..

. .

.

.

.

.

.

.

..

. .

P.62 F

F

F

F

P.63

I1 I2

x

.

.

.

x

xF1

P.63

I1 I2

x

.

.

.

x

xF2

P.63

I1 I2

x

.

.

.

x

xF1

P.63

I1 I2

x

.

.

.

x

xF2

P.63

P.63

Attractive force Repulsive force

P.63

N

S

vF

N

S

I

P.63

vF

AuroraP.63

P.64

P.64

The rod moves to LHS.

P.64

The rod moves to RHS.

P.64

No current on metal rod. The rod remains at rest.

P.65

X : North, Y : South

Out of the paper

More magnetic field lines

The force is reversed in direction

No change in direction

P.65

P.62

P.66

P.66

P.66

P.66

0

0 0 Anticlockwise

0

0 0 Clockwise

D.c. motor

F

-F

A couple is formed

Commutatorrotateswith the coil

P.67

Curren

t flo

ws fro

m A

to BP.67

P.67

Motor can bemore powerful

Use a strongermagnet

Use larger current

Increase number ofturns per unit length of coil

P.68

Use soft-iron core

x .

x

.

F

-F

Couple isconstant

P.68

N S

Several coils

Soft-iron core

Large numberof turns of wire

Increase power &run more smoothly

x

.

x

.x .

P.68

Loudspeaker

Soundwave

P.68

Solenoid

Paper coneCircularmagnet

P.68

SN

N

N

N

N N

N

N

P.68

P.68

P.70

P.70

P.71

P.71

P.71

P.71

P.71