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Introductory Physics 2 > Chapter 22 > Flashcards

Chapter 22 Flashcards

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1
Q

what is current?

A

the motion of charges through a material is called current

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2
Q

What happens when a Capacitor Discharges?

A

If we connect two plates of a charged capacitor with a metal wire, the charge on each decreases and they eventually become neutral: the capacitor discharges

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3
Q

What are Charge Carriers?

A

The charge that move in a current called “charge carriers”

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4
Q

Charge Carries are the motion of?

A

They are the motion of CONDUCTION ELECTRONS, which are free to move around, that forms a current in the metal

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5
Q

What is Random Thermal Motion?

A

The electron has frequent collisions with ions, but it undergoes no net displacement

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6
Q

What happens if a conductor is placed in an electric field?

A

The conduction electrons feel a force, they experience a net displacement in the opposite direction of the field

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7
Q

What is Drift Speed?

A

the drift speed (due to the electric field) is of the order of 10^-4m/s
- The drift speed os MUCH SMALLER than the average speed due to random thermal motion

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8
Q

What is the Speed due to Random Thermal Motion?

A

The speed due to random thermal motions is of the order 10^8m/s

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9
Q

What is the definition current?

A

Current is the rate at which charge moves through a wire, The total amount of charge delivered by a steady current (I) during a time interval (Δt) is…
I = Δq/Δt
SI Units = ampere (A) = 1A = 1C/s

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10
Q

What is conventional current?

A

The flow of positive charge (even though in metals it is the negative conduction of electron that actually flow)
- Electrons move in the direction opposite of conventional current

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11
Q

How are Current and Drift Speed related?

A
  • Charge carriers move in a wire of cross-sectional area A
  • The volume of the segment is AΔx
  • There are (n) charges carriers per unit volume, each with charge (q)
  • The total charge in the segment is the number of carriers times the charge per carrier:
    ΔQ = (nAΔΔx)q combined with drift speed…
    I = ΔQ/Δt = nAvq
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12
Q

What is the Law of Conservation of Current?

A

The current is the same at all points in a current-carrying wire
- The current leaving the bulb is exactly the same as the current entering the bulb

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13
Q

What are the two factors that determine current?

A
  1. the potential difference
    - adding a second battery increase the potential difference, which increase the current
  2. The properties of the wire
    - increasing the wires length decreases the current, and increasing its thickness increases the current
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14
Q

What is Ohm’s Law?

A

In most materials, including most metals, the current is proportional to the potential difference
I = ΔV/R

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15
Q

What is Resistance?

A 
The resistance (R) measures how hard it is to push charges through a wire. the larger the resistance, the harder it is to move charges
SI Units = ohms = 1Ω = 1V/A
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16
Q

What is an Ohmic Device?

A
  • The resistance is constant over a wide range of voltages, the relationship between current and voltage is linear, the slope of the I versus ΔV is 1/R
17
Q

What is a Non-Ohmic?

A

-The resistance changes with voltage or current, the relationship between current and voltage is nonlinear

18
Q

What is Resistivity and Resistance?

A

The resistance of an ohmic conductor is proportional to its length, L, and inversely proportional to its cross-sectional area, A:
R = pL/A
- The resistivity constant of proportionality (p) is called RESISTIVITY of the material
SI Units: Ωm

19
Q

How are Energy and Power related to each other?

A

The power supplied by the battery is the rate at which energy is transferred from the battery to the moving charges
P = ΔU/Δt = ΔqΔV/Δt = IΔV
P = E/t
SI Units of Power are Watts (W), 1W = 1J/s

20
Q

1 kWh is equivalent to what?

A

1kWh = 3.60*10^6J

Is the amount of energy required to supply 100W of power for 1 hour

21
Q

What is an Ammeter?

A

An Ammeter measures current, it is connect in series with the bulb, so that all the charge passing through the bulb also must pass through the meter

22
Q

What is a Voltmeter?

A

A Voltmeter measures voltage, it is connect in parallel with the bulb, to measure the potential difference across it

23
Q

What is a Circuit Diagram?

A

A circuit diagram is a logical picture of what is connected to what is connected to what
- The actual circuit may look quite different

24
Q

What is another name for Potential Difference across a battery?

A

Emf

25
Q

What is Kirchhoff’s Junction Law?

A

Junction Law: I1 = I2 + I3

ΣIin = ΣIout

26
Q

What is Kirchhoff’s Loop Law?

A

states the sum of the potential differences around any loop formed by the circuit must be zero
ΔVloop = ΣΔVi = 0

27
Q

What are Resistors in Series?

A

When resistors are connect in series, the equivalent resistance is always LARGER THAN each individual resistance
Req = R1 + R2 + R3 + …Rn

28
Q

What are Resistors in Parallel?

A

When resistors are connected in parallel, the equivalent resistance is always SMALLER THAN each individual resistance
Req = (1/R1 + 1/R2 + 1/R3 +…1/Rn)^-1

29
Q

What are Capacitor Circuits?

A

When a capacitor is connect to a battery, charge flows to the capacitor plates, increasing the potential difference
- Once the capacitor is fully charged, there is no further current, the amount of charge on the capacitor is given by…
Q = CΔVc

30
Q

What are Capacitors in Parallel?

A

When capacitors are connect in Parallel, the equivalent capacitance is aways LARGER THAN each individual capacitance
Ceq = C1 + C2 + C3 + …Cn

31
Q

What are Capacitors in Series?

A

When capacitors are connected in series, the equivalent capacitance is always SMALLER THAN each individual capacitance
Ceq = (1/C1 + 1/C2 + 1/C3 +….1/Cn)^-1

32
Q

What is another important formula for Potential Difference?

A

V = U/q or R = V^2/P

Introductory Physics 2 (10 decks)

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