Review Session #3Waves and ElectricityMINNETONKA HIGH SCHOOL | IB PHYSICS

Simple Harmonic Motion

a -x“Acceleration is proportional to the opposite of the displacement”

Dis

pla

cem

ent

Time

Vel

oci

ty

Time

Acc

eler

atio

n

Time

A

B

C

_____ vs Displacement

Displacement Displacement

Velocity Acceleration

Wave Equation

What is the wavelength of a 5.0 × 109 Hz microwave?

c = 3.00 × 108 m s-1

Standing Waves

# of Wavelengths Wavelength (m)

1 4 m6 m

4 m

9 m

12 m

Closed Pipe Resonance

L =

L =

L =

λ =

λ =

λ =

Open Pipe Resonance

L =

L =

L =

λ =

λ =

λ =

Calculating Frequency | Open Pipes

A open organ pipe is 2.1 m long and the speed of sound in the pipe is 341 m s-1. What is the fundamental frequency of the pipe?

Electromagnetic Spectrum

Try This

θ2

80°While aiming at a marble at the bottom of a fish tank filled with water (n2 = 1.33), you point so that you can measure the angle of your incident rays. What is the angle of refraction?

Try This

n2 = 1

n1 = 1.52

What’s the critical angle between glass and air?

θc

Wave Interference

Two speakers are separated by a distance of 5 meters, if they emit a coherent sound signal of 850 Hz. If the speed of sound is 340 m s-1, is this person in a maximum or minimum location

5 m

2.1 m

Polarized Light

Malus’ Law

The intensity of plane polarized light, at 30° to the vertical is I0. After passing through an analyzer at 60° to the vertical, what is the intensity measured?

Try This

Label these charges as positive (+) or negative (-)

Coulomb’s Law

A -5 C charge is placed 6 mm from a -5 C charge. Find the force between the two charges.

Electron Drift – Try This

𝐼 = 𝑛𝐴𝑣𝑞Suppose the current in a 2.5 mm diameter copper wire is 1.5 A and there are 5.01026 free electrons per cubic meter. Find the drift velocity

Elementary Charge = 1.6 × 10-19 C

Graphing Ohm’s Law

Find V and R for the resistors X and Y when the current is 2A

V

I

R

V

I

R

X

Y

Kirchhoff’s First LawThe total current coming into a junction must equal the total current leaving the same junction

5 A

3 A

5 A

9 A

2 A 4 A

(+5) + (-3) + (-2) = 0 (+5) + (-9) + (+5) = 0

Σ𝐼 = 0 (𝑗𝑢𝑛𝑐𝑡𝑖𝑜𝑛)Entering Junction ● Positive

Exiting Junction ● Negative

Kirchhoff’s First Law | Try This

6 A

5 A

3 A

1 A

2 A

Kirkoff’s Second Law

Σ𝑉 = 0 (𝑙𝑜𝑜𝑝)

8 V

12 V

1 V9 V

12 V

Negative to Positive Positive

Positive to Negative Negative Always Negative

Over Resistors:

Across Batteries

The Big Three

Ohm’s Law: If you know two of the three electrical properties: V, I, or R 𝑅 =

𝑉

𝐼

Kirchhoff’s Voltage Law Kirchhoff’s Current Law

Σ𝑉 = 0 (𝑙𝑜𝑜𝑝) Σ𝐼 = 0 (𝑗𝑢𝑛𝑐𝑡𝑖𝑜𝑛)

• Draw a loop• The voltage provided must equal

the voltage dissipated• Useful if you parallel branches to

solve for

• Calculate the current coming out of the battery (total current)

• If this splits into parallel branches, the total should still add up

Combining Resistors – Try This

4 Ω

6 Ω

4 Ω 6 Ω 8 Ω

Calculating Circuits - Series

R1 = 6 Ω

Vb = 12 V

I

R2 = 2 Ω Resistor V I R

R1

R2

Total

Calculating Circuits - Parallel

R2 = 3 Ω

V = 12 V

R1 = 6 ΩResistor V I R

R1

R2

Total

Combination Circuits - Simplify

R1 = 3 Ω

12 V

R2 = 6 Ω

R3 = 3 Ω

Resistor V I R

R1

R2

R3

Total

Ammeter

Hooked up in ____________ with the component being measured

Ideal Ammeter:

[R = ]A

What if Ammeter isn’t ideal?

A

10 V

What is the reading for the current flowing through the ammeter if it has an added resistance of 1 Ω?

R1 = 5 Ω R2 = 5 Ω

Voltmeter

V

Hooked up in ____________ with the component being measured

Ideal Voltmeter:

[R = ]

What if Voltmeter isn’t ideal?

V

R1 = 5 Ω

10 V

What is the reading for the voltmeter across R1 if it has an added resistance of 20 Ω?

R2 = 5 Ω

Try This

A

12 V

R1 = 3 Ω R2 = 6.5 Ω

V

R1 = 4 Ω

12 V

R2 = 2.5 Ω

Calculate the resistance of these non-ideal meters:

AmmeterReading 1.2 A

VoltmeterReading 7 V

Resistivity – Try This #2

A current of 4 A flowed through an 75 m length of metal alloy wire of area 2.4 mm2 when a p.d. of 12 V was applied across its ends. What was the resistivity of the alloy?

Potential Divider | Night Light

9.0 V

A light-dependent resistor (LDR) has R = 25 Ω in bright light and R = 22,000 Ω in low light. An electronic switch will turn on a light when its p.d. is above 7.0 V. What should the value of R2 be?

R1 R2

Electronic Switch

Potential Divider | Sprinkler System

9.0 V

A thermistor has a resistance of 250 Ω when it is in the heat of a fire and a resistance of 65,000 Ω in when at room temperature. An electronic switch will turn on a sprinkler system when its p.d. is above 7.0 V. What should the value of R1 be?

R1 R2

Electronic Switch

Batteries | Internal Resistance

10 Ω

0.5 Ω

1.2 A

What is the emf for a battery shown below?

ε

Magnetic Fields

Magnetic field lines point from _________ to _________

N S

A compass would align with these field lines

Remember the Right Hand Rule?

1 2Thumb points in direction of the current

Fingers point in direction of the field lines

Thumb points in toward the North Pole of the magnet

Fingers point in direction of the current

Right Hand Rule #3

Thumb points in direction of the current

Fingers point in direction of the field lines

Palm points in direction of the force

How do you represent a direction that’s perpendicular to the paper?

Into the paper Out of the paper

Force on a Current Carrying Wire

A current of 3.8 A in a long wire experiences a force of 5.7 × 10-3 N when it flows through a magnetic field of strength 25 mT. If the length of wire in the field is 10 cm, what is the angle between the field and current?

Force on a Moving Charge

What is the magnetic force acting on a proton (+1.6 × 10-19 C) moving at an angle of 32° across a magnetic field of 5.3 × 10-3 T at a speed of 3.4 × 105 m s-1?

Particles Moving Across Fields

magnetic field out of screen magnetic field into screen

+

+

-

-