P2 Electricity

Question 1

Explain what a thermistor is.

Answer 1

A type of resistor tha resistance changes depending on the temperature.
Resistance decreases as temperatureincreases.

Question 2

What is Power ?

& equasions used to calculate it.

Answer 2

How quickly energy can be transfered.
E=Pt / P=IV / E=QV

Question 3

What is and Electric current?

(+ units)

Answer 3

The flow of electric charge.
Measured using an ammeter, Amps(A)
High current = lots of electrons moving fast
Low current = few electrons slow moving

Question 4

What are electric circuts?

Answer 4

They transfer energy, energy is carried around the circut by electrons.
Circuts have different componants to alow them to complete energy transfer.

Question 5

What is Potential Difference?

(+ units)

Answer 5

The amount of energy carried by each electron.
Measured using a voltmeter in volts (V).
energy per unit charge

Question 6

What are rules for paralel circuts?

Answer 6

1) current in each branch of the circut has to add up to total current
2) Potential difference of componant in a branch is the same as battery.

Question 7

What are the rules for series circuts?

Answer 7

1) cells in series add up
2) current is the same everywhere
3) p.d. across componants adds up to p.d. across the battery

Question 8

What is an IV characteristic graph?

Answer 8

A grap that plots current(y-axis) against p.d. (x-axis)
all componants can have an IV characteristic graph.
If current and P.d. are directly preportional on the graph it is an ohmic conductor.

Question 9

Explain what an LDR is.

Answer 9

A light dependant resistor is a resistor that depends on light intensity. In bright light the resistance falls.
Componant in circut

Question 10

What causes resistance?

Answer 10

As electrons flow through the wire they collide with metal ions in the wire. This slows them down causeing resistance.

Question 11

What is an Ohmic conductor?

Answer 11

Obeys ohms law but temperature cant change.

Question 12

What is Resistance like in a series and Paralel circut?

Answer 12

Series - adds up
Paralel- resistance is allways less than bc current has multiple paths can flow.

Question 13

What is the Equasion for resistance, current and P.d?

Answer 13

P.d. = current xresistance
V=IR
volts(v) Amps(A) Ohms(Ω)

Question 14

What is ohms law?

Answer 14

says - “p.d. is directly perportional to current provided the temperatre is constant “

Question 15

Complete the table

|series |paralel
current| | |
p.d. | | |
resistance | |

Answer 15

current| same|split|
p.d.| split | same|
resistance| adds up |less than|

Question 16

What factors effect resistance of a metal wire?

Answer 16

Temperature- temp ↑ resistance ↑bc likely hood of metal ions colliding ↑
Length - longer wire= more metal ions = more collisions = more resistance
Area - ↑ area ↓resistance more routes for charge
Material Type - more/ less resistive

Question 17

Explain what a diode is.

Answer 17

Diodes only alow current to flow in one direction. Resistance depends on the direction of the current, high resistance depends on the direction of the current.

Question 18

What happens if there is a break in the to types of circut?

Answer 18

In SERIES circut (if breaks) the current wont flow bc the circut isnt one complete loop/
In PARALEL circuts switches can turn branches on and off and depending on which branch breaks the circut could still work.

Question 19

Describe these quantities and give units.

Energy
Charge
Power

(in terms of electricity)

Answer 19

Energy : gets transfered around the circut (J)
Charge : positive, negative, neutral (C) Coulombs
Power : how quickly energy is transfered (W)watts

Question 20

What is the resolution?

Answer 20

Resolution of a device is the smallest change a device can detect.

Question 21

Explain circut symbol for a variable resistor

Explain what a variable resistor is.

Answer 21

(rectange/ resistor with an arrow pointing north east or top right)
The slider on a variable resistor is used to change the length of the coil so current can be increased or decreased, varied.

eg. dimmer light, volume control.

Question 22

What equasion links time, charge and current?

Answer 22

Charge = current x time
(Q)coulombs (A)amps (s)seconds
Q=It I =Q/t t=Q/I

Question 23

What is resistance?

(+ units) (+ high / low resistance = ….)

Answer 23

How hard it is for charge to flow through a componant. Measured by calculation in ohms(Ω).
High resistance - hard for electrons to flow - small current
Low Resistance - easy for electrons to flow - large current

Question 24

What equasion links Energy, Charge and P.d?

Answer 24

Energy = P.d. x Charge
(J) joules (V) volts (C) coulombs
E = QV Q =E/V V=E/Q

Question 25

Explain the IV characteristic graph for a fillament lamp .

Answer 25

Resistance is not constant so it is not an ohmic conductor.
Curves show that resistance is ↑ because = current ↑ temp↑ so metal ions colliding ↑ (becomes more vigorous) = resistance.

Question 26

Explain the IV characteristic graph for a diode.

Answer 26

current can only flow in one direction on this graph.
Current is 0 in the reverse direction.

Question 27

Explain the IV characteristic graph for a Resistor.

Answer 27

Resistors are ohmic conductors. The p.d. and current are preportional.

Question 28

How does the lenght of a wire effect resistance in the circut.

Answer 28

As the length of the wire increases so does the resistance this means it is directly preportional.