Physics with Calculus II

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Physics with Calculus II
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Fridays lab RC time constant
This is a quote from a movie. Can you answer any
of these questions?

• What is the name of the movie?
• Who is the actor speaking?
• What role is he playing?
• Who is he talking about?

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Where weve been

• Mechanics
• The Electric Field
• Gausss Law
• Electric Potential (V)
• Capacitance
• Current Resistance
• DC Circuits
• Magnetic Field

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Ch 30 Introduction
Because currents produce magnetic fields, we
expect them to interact with one another through
these fields. Practical devices can be
constructed from these interactions. Some of the
possibilities are discussed in this chapter.
This chapter looks at current in a wire as a
source of Magnetic Field (B) Section 8 discusses
Magnetism in Matter Be sure to read Section 9
on B of the Earth.
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Where were going
Ch 30 Sources of The Magnetic Field (30.1) The
Biot-Savart Law (30.2) F mag between two parallel
conductors (30.3) Amperes Law (30.4) Magnetic
Field of Solenoid (30.5) Magnetic Flux
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(30.1) The Biot-Savart Law
If a wire carries a STEADY current, the B at
point p associated with wire element ds has
these properties
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(30.1) The Biot-Savart Law, contd

• The vector, dB, is ? both to ds (in direction of
  I) and r (directed from ds to p)
• The magnitude of dB is ? 1 / r2, where r is dist
  ds to p.
• The magnitude of dB is ? I and magnitude of
  length element ds.
• The magnitude of dB is ? sin ?, where ? is angle
  between ds and r.

• See Figure 30.1, page 938

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(30.1) The Biot-Savart Law, contd
Example 30.1, page 940 Find B for long, straight
wire
Example 30.2 page 941 B due to I in circular
loop
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(30.2) Fmag between two parallel conductors
Each conductor produces a magnetic field
From ch 29
I in same direction attract I in opposite
direction repel
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(30.3) Amperes Law
Valid only for steady currents Useful only when
current configuration is highly symmetrical.
Compare Ex 30.4, page 947 with Ex 30.1
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(30.4) Magnetic Field of Solenoid
We know uo from ch 29
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(30.5) Magnetic Flux
Where
Compare
Problem 30.33
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• The End