Flashcards in Chapter 22 Deck (32):

1

## what is current?

### the motion of charges through a material is called current

2

## What happens when a Capacitor Discharges?

### 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

3

## What are Charge Carriers?

### The charge that move in a current called "charge carriers"

4

## Charge Carries are the motion of?

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

5

## What is Random Thermal Motion?

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

6

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

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

7

## What is Drift Speed?

###
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

8

## What is the Speed due to Random Thermal Motion?

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

9

## What is the definition current?

###
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

10

## What is conventional current?

###
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

11

## How are Current and Drift Speed related?

###
- 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

12

## What is the Law of Conservation of Current?

###
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

13

## What are the two factors that determine current?

###
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

14

## What is Ohm's Law?

###
In most materials, including most metals, the current is proportional to the potential difference

I = ΔV/R

15

## What is Resistance?

###
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

16

## What is an Ohmic Device?

### - 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

## What is a Non-Ohmic?

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

18

## What is Resistivity and Resistance?

###
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

## How are Energy and Power related to each other?

###
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

## 1 kWh is equivalent to what?

###
1kWh = 3.60*10^6J

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

21

## What is an Ammeter?

### 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

## What is a Voltmeter?

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

23

## What is a Circuit Diagram?

###
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

## What is another name for Potential Difference across a battery?

### Emf

25

## What is Kirchhoff's Junction Law?

###
Junction Law: I1 = I2 + I3

ΣIin = ΣIout

26

## What is Kirchhoff's Loop Law?

###
states the sum of the potential differences around any loop formed by the circuit must be zero

ΔVloop = ΣΔVi = 0

27

## What are Resistors in Series?

###
When resistors are connect in series, the equivalent resistance is always LARGER THAN each individual resistance

Req = R1 + R2 + R3 + ...Rn

28

## What are Resistors in Parallel?

###
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

## What are Capacitor Circuits?

###
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

## What are Capacitors in Parallel?

###
When capacitors are connect in Parallel, the equivalent capacitance is aways LARGER THAN each individual capacitance

Ceq = C1 + C2 + C3 + ...Cn

31

## What are Capacitors in Series?

###
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