4.1 Electricuty

Question 1

Electric current is the rate of flow of charge what is the equation for that

Answer 1

I = change in charge ( Q ) / Change in time (T)

Question 2

What is conventional current

Answer 2

Current flows from positive to negative terminal

Question 3

What is electron flow

Answer 3

In reality electrons flow from negative to positive terminal

Question 4

What is kirchoff’s first law

Answer 4

The sum of current in and out of a junction algebraically are the same

Question 5

What is electric current and what is the equation

Answer 5

The rate of flow of charge
Current= change in charge/ change in time

Question 6

What does e.m.f stand for and what is is

Answer 6

electromotive force.
It is the chemical energy to electrical energy per unit charge

Question 7

What does p.d stand for and what is it’s definition

Answer 7

Potential difference and it is the electrical energy to other forms of energy

Question 8

How to calculate the e.m.f

Answer 8

E.m.f = energy transferred/ charge

Question 9

NEVER BACK DOWN NEVER WHAT???

Answer 9

NEVER GIVE UPヾ(⌐■_■)ノ♪

Question 10

Draw the I-V graph for a lamp

Answer 10

[draw it]

Question 11

Draw the I-V graph for a diode

Answer 11

[draw it]

Question 12

What is resistivity

Answer 12

And objects opposition to the flow of charge

Question 13

What is the equation for resistivity

Answer 13

Resistivity = resistance X area / length

Question 14

what is the rule for current in a series circuit

Answer 14

series circuit, the current is the same for all components

Question 15

what is the rule for p.d in series circuit

Answer 15

p.d is shared between all components

Question 16

what is the rule for resistance in series circuit

Answer 16

total resistance is the sum of all resistances

Question 17

what is the rule for p.d in parallel circuit

Answer 17

p.d for cell/battery is the p.d for each branch

Question 18

what is the rule for current in parallel circuits

Answer 18

the current is split between the branches

Question 19

what is the rule for resistance in parallel circuits

Answer 19

The sum of the resistance in parallel circuits is equal to the sum of the inverse of each individual resistances

1/Rt= 1/R1 + 1/R2 + 1/R3

Question 20

what is resistance

Answer 20

the opposition to current

Question 21

What is drift velocity

Answer 21

The net movement of electrons

Question 22

Resistance =

Answer 22

Potential difference/current

Question 23

Kirchhoff’s second law

Answer 23

The sum of the e.m.f is equal to the sum of the potential difference in series

Question 24

What is potential difference

Answer 24

The work done per unit charge

Question 25

What is one coulomb

Answer 25

The amount of charge that passes in 1 second when the current is 1 amp

Question 26

Energy transferred electricity equations

Answer 26

W=VQ

Question 27

Define potential difference of 1 volt

Answer 27

1 joule of energy transferred per coulomb

Question 28

What is the mean drift velocity

Answer 28

The average velocity of the charge carriers

Question 29

What is the mean drift velocity equation

Answer 29

I = Anev Current = Cross sectional area x number density of electrons x size of charge in one electron x mean drift velocity’s

Question 30

Equation for resistance is

Answer 30

R= V/I

Question 31

What 3 things does resistance depend on?

Answer 31

-Length(L) the longer the wire the more difficult it is for current to flow -Area (A) the wider the wire the easier it will be for electrons to pass through -Resistivity (ρ) depends on material wire is made from how easy electrons flow through a material

Question 32

Resistivity definition and unit

Answer 32

The resistance of a 1m length with a 1m^2 cross-sectional area -Ohmmeters is unit

Question 33

What is ohms law

Answer 33

If the temperature is constant the current through an ohmic conductor is directly proportional to the potential difference

Question 34

Why is the I-V characteristic for a metallic conductor a straight line

Answer 34

-At a constant temperature the current is directly proportional to the potential difference - metallic conductors are ohmic- they have constant resistance just so long as the temperature doesn’t change

Question 35

Why is it characteristic for lamp curved

Answer 35

Current flowing though lamp increases its temperature. So the resistance increases

Question 36

Why does the resistance of a metal increase with temperature

Answer 36

Heating makes it harder for electrons to move about. The ions vibrate more when heated so the electrons collide with them more often. Ionising energy gets lost to other forms

Question 37

Why do semi conductors resistance decrease as the potential difference increases

Answer 37

Semi conductors have higher resistance because there are fewer charge carriers available. If energy is supplied more charge carriers are released so resistivity decreases. So they are good for detecting changes

Question 38

Power definition

Answer 38

Power is the rate of transfer of energy or one joule of work done per second

Question 39

Formula for power in electrical circuits

Answer 39

P=IV

Question 40

Give equation 2 for power

Answer 40

Power = (Voltage)^2 / Resistance P= I^2 R

Question 41

Give Equation 3 for power

Answer 41

Power = (Current)^2 X Resistance

Question 42

An equation for power that links work done and time

Answer 42

P= W ÷ t Power = work done ÷ time

Question 43

Explain how voltage is affected when temperatures change for thermistors

Answer 43

componentAs temperature of thermistor increases, resistance of thermistor decreases Total resistance of circuit decreases and current increases Greater proportion of p.d. across fixed resistor Reading on the voltmeter will increase

Question 44

Copper is a metal, carbon is a semiconductor and ceramic is an insulator. Describe the difference between these three materials in terms of the number density n free electrons. Include an explanation of the term number density.

Answer 44

n = number of (free) charge carriers per unit volume The larger the value of n, the better the conduction Copper has a larger n than carbon which has a larger n than ceramic