Section 16.4 Force On Current-carrying Conductor In Magnetic Field

Section 16.4 Force on current-carrying conductor in magnetic field • Fleming's left-hand rule • Factors affecting the magnitude of force on current-carrying conductor • Turning effect of coil © Manhattan Press (H.K.) Ltd.

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16.4 Force on current-carrying conductor in magnetic field (SB p. 120)

Force on current-carrying conductor in magnetic field

current-carrying conductor experiences force in magnetic field

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Discussion 5 © Manhattan Press (H.K.) Ltd.

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16.4 Force on current-carrying conductor in magnetic field (SB p. 121)

Force on current-carrying conductor in magnetic field

Expt. 16D Magnetic force on a currentcarrying conductor

d.c. power supply

magnet rider

Fleming's apparatus © Manhattan Press (H.K.) Ltd.

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16.4 Force on current-carrying conductor in magnetic field (SB p. 121)

Force on current-carrying conductor in magnetic field either • direction of current • poles of magnet reversed → moves in opposite direction

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16.4 Force on current-carrying conductor in magnetic field (SB p. 121)

Fleming's left-hand rule Fleming's left-hand rule force

field

current © Manhattan Press (H.K.) Ltd.

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16.4 Force on current-carrying conductor in magnetic field (SB p. 122)

Fleming's left-hand rule force field

current current CAL Workshop 1

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Force on currentcarrying conductor in magnetic field

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16.4 Force on current-carrying conductor in magnetic field (SB p. 122)

Factors affecting the magnitude of force on current-carrying conductor magnetic force ↑ by (1) Use stronger magnet

current

(2) ↑ no. of turns of wire (3) ↑ current © Manhattan Press (H.K.) Ltd.

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16.4 Force on current-carrying conductor in magnetic field (SB p. 123)

Turning effect of coil

field current force

turning effect Thinking 6 © Manhattan Press (H.K.) Ltd.

principle of motors & meters 8

16.4 Force on current-carrying conductor in magnetic field (SB p. 123)

Example 2: A conducting rod is placed in each of the following open circuits. State the motion of the conducting rod. (a)

(b)

To the right.

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Solut ion

To the left.

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16.4 Force on current-carrying conductor in magnetic field (SB p. 123)

Example 2: (Cont) (c)

(d)

To the right.

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Solut ion

At rest.

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16.4 Force on current-carrying conductor in magnetic field (SB p. 124)

Class Practice 3: A copper rod is placed on an open circuit. When the switch is closed and the resistance of the rheostat is increased gradually, state and explain the motion of the rod when it is placed at positions AB and CD. Ans wer

magnetic field region © Manhattan Press (H.K.) Ltd.

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16.4 Force on current-carrying conductor in magnetic field (SB p. 124)

Class Practice 3: At AB, the rod does not move because there is no magnetic field around it. At CD,

magnetic field region

Ans wer

the rod moves to the right according to Fleming's left hand rule. It moves at a decreasing acceleration because the current is decreasing.

Thinking 7 © Manhattan Press (H.K.) Ltd.

Thinking 8 12

To section 16.5

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16.4 Force on current-carrying conductor in magnetic field (SB p. 120)

Discussion 5:

What happens when a current-carrying conductor is placed in a magnetic field? Discuss with your classmates. (Hint: A magnet experiences a force near another Ans magnet.) wer

The current-carrying conductor experiences a force in a magnetic field. Return to

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16.4 Force on current-carrying conductor in magnetic field (SB p. 120)

Thinking 6

Ans wer

The figure shows three long current-carrying straight wires P, Q and R. The magnitude of the current flowing through each wire is the same. Draw a diagram to represent the direction of the resultant force acting on P.

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16.4 Force on current-carrying conductor in magnetic field (SB p. 120)

Thinking 6 (Cont)

Return to

Text © Manhattan Press (H.K.) Ltd.

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16.4 Force on current-carrying conductor in magnetic field (SB p. 124)

Thinking 7

In Class Practice 3, if both the directions of the magnetic field and the terminals of the cell are reversed, does the motion of the rod at positions AB and CD change? Ans wer

At AB, the rod still does not move. At CD, the rod still moves to the right. © Manhattan Press (H.K.) Ltd.

magnetic field region Return to

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16.4 Force on current-carrying conductor in magnetic field (SB p. 124)

Thinking 8 When lightning strikes, negative charges flow from a cloud to the ground. Explain why the strike is deflected to the west. Ans The downward flow of negative wer in a lightning strike is charges equivalent to an upward flow of current. With the earth's magnetic field pointing from the south to the north, by Fleming's left hand rule, the negative charges in the lightning strike would Return to be deflected towards the west, except at the Arctic and the Antarctic of the earth. Text © Manhattan Press (H.K.) Ltd.

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