Exam 4 Phy 131

Front 1

Combining a Series: Resistance

Back 1

Rtot=R1+R2+…

Front 2

Combining a Series: Voltage

Back 2

Vtot=V1+V2+…

Front 3

Combining a Series: Currents

Back 3

Itot=I1=I2=…

Front 4

Combining a Parallel: Resistance

Back 4

1/R_tot =1/R1 +1/R2 +⋯

Front 5

Combining a Parallel: Voltage

Back 5

Vtot=V1=V2=…

Front 6

Combining a Parallel: Currents

Back 6

Itot=I1+I2+…

Front 7

Ohm’s Law

Back 7

I=V/R or R=V/I OR V=RI

Front 8

Kirchoff’s Loop Law

Back 8

The sum of the voltage rises and drops around any closed path is equal to 0.

Front 9

Kirchoff’s Node Law

Back 9

The current that enters a node equals the current that leaves that node.

Front 10

SI Units: Voltage

Back 10

Volts(V) or Joules per Coulumb (J/C)

Front 11

Combining a Series for a Capacitor: Capacitance

Back 11

1/Ctot =1/C1 +1/C2 +⋯

Front 12

Combining a Series for a Capacitor: Voltage

Back 12

Vtot=V1+V2+…

Front 13

Combining a Series for a Capacitor: Charge

Back 13

Qtot=Q1=Q2=…

Front 14

Combining a Parallel for a Capacitor: Capacitance

Back 14

Ctot=C1+C2+…

Front 15

Combining a Parallel for a Capacitor: Voltage

Back 15

Vtot=V1=V2=…

Front 16

Combining a Parallel for a Capacitor: Charge

Back 16

Qtot=Q1+Q2+…

Front 17

Capacitance

Back 17

C=Q/V or V=Q/C OR Q=CV

Front 18

SI Units: Capacitance

Back 18

Farads(F) or Coulomb per Volt (C/V)

Front 19

What is a capacitor?

Back 19

A device used to store an electric charge that consists of one or more pairs of conductors separated by an insulator.

Front 20

What does a capacitor do?

Back 20

It stores charge.

Front 21

How is a capacitor different from a battery?

Back 21

A capacitor stores charge while a battery creates charge through a chemical process.

Front 22

When a capacitor is in parallel with another capacitor they have an equal amount of ______.

Back 22

volts

Front 23

When a capacitor is in series with another capacitor they have an equal amount of _____.

Back 23

charge

Front 24

You can determine the voltage of the battery in a capacitor problem using _____.

Back 24

Kirchoff’s Loop Law

Front 25

Steps to determine current in problem using Kirchhoff's Laws

Back 25

1. Draw the current diagram using arbitrary arrows

2. Use Kirchhoff's Node Law to write an equation for the current. (There will be 1 fewer equation than the amount of nodes in the problem)

3. Use Kirchhoff's Loop Law to write an equation for the voltage in terms of resistance and current. (For all the interior loops)

4. Rewrite the equations in standard form.

5. The constants on the LHS will form one matrix [A], and the constants on the RHS will form another [B].

6. Solve for I using the following formula: I=A^(-1)*B

7.Redraw a new current diagram for the circuit to match the new values.

Front 26

Standard form for equations

Back 26

Variables on the LHS, Constants on the RHS

Front 27

Interior Loop

Back 27

A loop that does not have a smaller loop inside of it.

Front 28

When the voltage across a resistor decreases the resistance of the resistor _____.

Back 28

stays the same

Front 29

When the voltage across a resistor decreases the current thru the resistor _____.

Back 29

decreases

Front 30

When the voltage across a capacitor decreases the capacitance of the capacitor _____.

Back 30

stays the same

Front 31

When the voltage across a capacitor decreases the current of the capacitor _____.

Back 31

decreases

Front 32

The capacitance of a capacitor depends on what?

Back 32

The capacitance of a capacitor depends on the geometry of the capacitor and the materials from which it was constructed.

Front 33

The resistance of a resistor depends on what?

Back 33

The resistance of a resistor depends on the geometry of the resistor and the materials from which it was constructed.

Front 34

What is the sum of voltage across the resistor and the voltage across the capacitor equal to after the switch is closed?

Back 34

The voltage of the battery.

Front 35

Mathematical Relationship between Current and Charge

Back 35

I=dQ/dt

Front 36

The slope from the charge on the capacitor v. time graph equals what?

Back 36

The current flowing thru the wire.

Front 37

The current flowing in the circuit _____ as time passes. This means that the current starts out _____ and ends up _____. This tells you the slope of the charge v. time graph starts out _____ and ends up _____. The charge on the capacitor _____ as time passes, this means that the charge on the capacitor starts out _____ and ends up _____.

Back 37

decreases, high, low, steep, shallow, increases, low, high

Front 38

Charge v. Time Graph (Charging)

Back 38

Front 39

Voltage across Capacitor v. Time Graph (Charging)

Back 39

, Vc

Front 40

Voltage across Resistor v. Time Graph (Charging)

Back 40

, Vr

Front 41

Current thru Resistor v. Time Graph (Charging)

Back 41

Front 42

What is the limiting factor that keeps the capacitor from charging instantaneously?

Back 42

Voltage

Front 43

Equation of the Charge of a Capacitor: Charging

Back 43

Q=Vbatt*C(1-e^(-t/RC))

Front 44

Equation of the Voltage across a Capacitor: Charging

Back 44

Vc=Vbatt(1-e^(-t/RC))

Front 45

Equation of the Voltage across a Resistor: Charging

Back 45

Vr=Vbatt*e^(-t/RC)

Front 46

Equation of the Current thru a Resistor: Charging

Back 46

I=(Vbatt/R)*e^(-t/RC)

Front 47

Charge v. Time Graph (Discharging)

Back 47

Front 48

Voltage across Capacitor v. Time Graph (Discharging)

Back 48

Front 49

Voltage across Resistor v. Time Graph (Discharging)

Back 49

, the same as current thru a circuit

Front 50

Current thru Resistor v. Time Graph (Charging)

Back 50

, current thru the circuit

Front 51

Equation of the Charge of a Capacitor: Discharging

Back 51

Q=Vbatt*C*e^(-t/RC)

Front 52

Equation of the Voltage across a Capacitor: Discharging

Back 52

Vc=Vbatt*e^(-t/RC)

Front 53

Equation of the Voltage across a Resistor: Discharging

Back 53

Vr=-Vbatt*e^(-t/RC)

Front 54

Equation of the Current thru a Resistor: Discharging

Back 54

I=(-Vbatt/R)*e^(-t/RC)

Front 55

Like magnetic poles _____.

Back 55

repel

Front 56

Opposite magnetic poles _____.

Back 56

attract

Front 57

What happens when you break a magnet in half?

Back 57

You get two weaker magnets.

Front 58

What do magnets attract?

Back 58

iron

Front 59

Magnetic fields ______ from north poles.

Back 59

diverge

Front 60

Magnetic fields ______ on south poles.

Back 60

converge

Front 61

Right Hand Magnetic Field Rule

Back 61

The right hand rule states that, to determine the direction of the magnetic field , you point the thumb of the right hand in the direction of the current, and your fingers curl in the direction of the magnetic field.

Front 62

Magnetic field lines are _____ to the magnetic field which circles the wire.

Back 62

tangent

Front 63

The further away from the magnetic field, the _____ the field line.

Back 63

smaller

Front 64

Magnetic Field Equation

Back 64