Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Lower Sixth Physics > Electricity > Flashcards

Electricity Flashcards

(52 cards)

Start Studying
1
Q

define electric current

A

electric current (I) is the rate of flow of charged particles
or
rate of flow of charge per unit time

I=Q/t

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

define potential difference

A

potential difference (V) is the energy transferred per unit charge between two points in a circuit

V=E/Q

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is resistance

A

resistance (R) is a measure of how difficult it is for charge carriers to pass through a component.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

define resistance

A

resistance is the opposition that a substance offers to the flow of electric current

R=V/I

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the Ohm’s law

A

Ohm’s law is obeyed when the current is directly proportional to the potential difference across, given that the physical conditions stay the same (e.e. temperature)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is an ohmic conductor

A

an ohmic conductor is a conductor that obeys Ohm’s law

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the principle of charge conservation

A

the principle of charge conservation states that the total electric charge in a closed system does not change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is Kirchoff’s first law

A

Kirchoff’s first law states the total current flowing into a junction is equal to the current flowing out of that junction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

current in a series circuit

A

current the same everywhere in a series circuit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

current in a parallel circuit

A

current splits into separate quantities in each branch and adds back when the branches join back
or
the sum of the currents in each parallel set of branches is equal to the total current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is Kirchoff’s second law

A

Kirchoff’s second law states that the sum of all the voltages in a series circuit is equal to the battery voltage
or the sum of all voltages in a loop is zero

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

potential difference in series circuit

A

the p.d. is shared across all elements in the circuit, therefore the total sum of the voltages across all elements is equal to the supply p.d.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

potential difference in parallel circuit

A

the potential difference across each branch is the same

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

resistance in a series circuit

A

RT = R1 + R2 + R3 + Rn

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

resistance in parallel circuit

A

1/RT= 1/R1+ 1/R2+ 1/R3+ 1/Rn

1/RT= R2/ R1R2 + R1/ R1R2

1/RT= (R1+R2)/ R1R2

RT = R1R2/R1+R2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

derive the formula for resistance in a series circuit

A

say there are 3 resistors in series
R1 R2 & R3
V=IR
V-supply=IRT, V1=IR1, V2=IR2, V3=IR3
K2L says the sum of voltages in series is equal to supply voltage
IRT =IR1+IR2+IR3
IRT =I(R1+R2+R3)
divide both sides by I
RT = R1 + R2 + R3
therefore R1+R2+R3 is total resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

derive the formula for resistance in a parallel circuit

A

say there are 3 resistors in parallel
R1, R2 & R3
V=IR -> I=V/R
V-supply=IRT, V1=IR1, V2=IR2, V3=IR3
using K1l, we know that p.d. in each branch is equal to V-supply
I=I1+I2+I3
I=V/R1+V/R2+V/R3
divide both sides by V
I/V=1/R1+1/R2+1/R3
I/V=1/RT
therefore,
1/RT = 1/R1+1/R2+1/R3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is power

A

energy transferred over time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

formulas for power

A

power = voltage * current (P=IV)

power = (V=IR) * current
power = current^2 * resistance

power = voltage * (I=V/R)
power = voltage^2 / resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

formula for energy transferred

A

energy transferred = power * time

since P=IV
then, energy transferred = current * voltage * time
E=ITV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

current-voltage graph for a ohmic conductor

Study These Flashcards
A

-proportional
-linear
-straight line through the origin

22
Q

current-voltage graph for a semiconductor diode

Study These Flashcards
A

-conducts/allows current in one way only
-only allow current flow easily when past the threshold voltage
-negative p.d. has extremely high voltage
-the graph has an extremely low gradient from negative p.d. to the threshold voltage, the graph spikes off when it reaches the threshold p.d.

23
Q

current-voltage graph of a filament wire bulb

Study These Flashcards
A

-as p.d. increases, current increases
-more current, more flow of electrons
-more electrons colliding with the metal lattice of the wire
-metallic lattice gain energy and heats up, ions vibrate more rigorously
-if the metal lattice vibrate more, more collisions with electrons
-hence increase in resistance
-graph obeys Ohm’s law at low currents
-graph curves at larger currents

24
Q

current-voltage graph of a NTC thermistor

Study These Flashcards
A

-opposite of filament bulb
-as p.d. increases, current increases, temperature increases
-increase in temperature, causes electrons to be released from the atoms, therfore an increase in charge carriers
-decrease in resistance
-graph obeys Ohm’s law at low currents
-graph curves at larger currents

25
define resistivity
-resistivity is the measure of how easily a material conducts electricity -product of resistance and cross-sectional area divided by length -resistivity will give the value of resistance through a length of 1m and cs area of 1m^3
26
relationships with resistance
-proportional to length -inversly proportional to cross-sectional area -changes with each material -increases with temperature
27
What is the charge carrier density?
The number of charge carriers per unit volume for a material
28
What is drift velocity?
The average speed at the charge carriers move along the conductor
29
What is the charge of electrons
1.6 x10^-19 C
30
Potential along a uniform current-carrying wire
R= pl/A For a uniform current-carrying wire, resistivity and cross sectional area stays the same As length increases, resistance increases V=IR As resistance increases, p.d. increases
31
What is a potential divider circuit
A circuit with several resistors in series connected across a voltage source, to produce a required fraction of source p.d.
32
What is internal resistance
Caused by electrons colliding with atoms inside the battery, causing energy to be lost before electrons even leave the battery
33
What is electromotive force
Energy transferred by a cell per coulomb of charge
34
Explain how some metals and semiconductors decrease in resistance
Temperature increases Atoms gain energy Electrons are released (thermionic emmision) Increase in charge carriers available Decrease in resistance
35
How do LDRs work
Made from photoconductive materials Electrons are released in presence of light Resistance decrease
36
State the equation used to calculate the resistivity of a wire
ρ = RA/l R = resistance A = cross-sectional area l = length of wire
37
How does the resistance of a wire change when the cross-sectional area decreases?
The resistance of a wire is inversely proportional to the cross-sectional and so as the area decreases, the resistance will increase.
38
How does the resistance of a wire change when the length is decreased?
The resistance of a wire directly proportional to the length of the wire, so as the length decreases the resistance decreases proportionally.
39
What is the unit of resistivity?
Ωm Ohm - Metres
40
How do you measure the cross-sectional area of a thin wire?
Using a micrometer, measure the wire’s diameter in at least three different places along the wire. Use the average diameter in the circular area equation.
41
Suggest how the length of conducting wire can be varied when carrying out the experiment (CP2).
One end of the wire can be fixed and the other end can be connected to the circuit using a crocodile clip. The length of conducting wire can be changed by varying the position of the crocodile clip.
42
What device is used to measure the potential difference across the wire, and how is it connected?
A voltmeter, which should be connected in parallel across the wire.
43
What device is used to measure the current flowing through the wire, and how is it connected?
An ammeter, which should be connected in series with the wire.
44
Why should the power supply be switched off between readings?
The temperature of the wire should remain constant throughout the experiment. Switching the power supply off between readings will mitigate heating of the wire, during the experiment.
45
Why should the temperature of the wire remain constant throughout this experiment (CP2)?
Temperature changes can affect the resistance of the wire. In this experiment, temperature is a control variable
46
Why does the resistance of a wire increase when its temperature increases?
As temperature increases, the metal ions gain more kinetic energy and so vibrate more. These vibrating ions make it harder for charges to pass through the wire and so the wire’s resistance increases.
47
How can the resistivity of a wire be determined from a graph of resistance against length?
The gradient of the graph will be R/L and so by multiplying the gradient by the wire’s cross-sectional area, you will obtain the wire’s resistivity.
48
Why should the current used in this experiment be kept low?
As current increases, the temperature of the wire will increase. By keeping the current low, the heating effect on the wire is kept to a minimum.
49
Suggest how you could ensure that your length measurements are taken from the same position each time.
A metre ruler could be taped in place below the fixed wire.
50
What factors lead to uncertainties in this experiment?
There will be resistance between the crocodile clips and wire as well as at the contact of the leads and the power supply. There may also be a zero error due to the positioning of the ruler and crocodile clip at the zero end.
51
What device could replace the voltmeter and ammeter in this experiment?
Instead of a voltmeter and ammeter, a multimeter could be used to measure the current, potential difference and resistance. Note that this may lower the resolution of your data depending on the number of significant figures provided by the devices you have available.
52
What is the method to determine the electrical resistivity of a material?
* At various points along the wire measure the diameter, d, repeat at 90* angles at the same point, get about 6 readings and find average - check for zero error on micrometre * Find cross-sectional area, A, of wire as: A = (πd^2)/4 * Connect circuit : battery, switch, ammeter in series, voltmeter in parallel * At 10cm intervals from crocodile clip, touch wire with probe, record voltage, v, and current, I, readings on voltmeter and ammeter respectively * Calculate Resistance R, as 𝑉/I * Measure length of wire, L, from one crocodile clip to the other, using a ruler * Vary L by changing position of the crocodile clips along the wire, and record corresponding values of R * Plot R (y axis) against L and draw line of best fit with equation: R = ρL/A

Lower Sixth Physics (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions