Electricity

Question 1

e=

Answer 1

1.6x10 to the power of - 19 coulombs

Question 2

1 amp =

Answer 2

1 coulomb per second

Question 3

Equation:

Current (A) =

Answer 3

Charge (C) / time (s) –> I = Q/T

Question 4

Definition of current

Answer 4

The rate of flow of charged particles

Question 5

What kind of particles run in wires

Answer 5

Electrons

Question 6

What kind of particles run in electrolytes

Answer 6

Ions

Question 7

What direction does current flow in a conventional current

Answer 7

From positive to negative

Question 8

What direction do electrons flow in

Answer 8

From negative to positive

Question 9

How many amps is 1 mA

Answer 9

0.001A

Question 10

Kirchhoff’s first law states that:

Answer 10

The sum of the currents flowing into any point in a circuit is equal to the sum of the currents flowing out of that point (based on the law of conservation of charge)

Question 11

What is 1 Amp

Answer 11

1 coulomb of charge passing a point in 1 second (1C/s)

Question 12

What is 1 Volt

Answer 12

1 joule (electrical potential energy) transferred per coulomb

Question 13

What is 1 Watt

Answer 13

1 joule per second (power)

Question 14

How many amps is 1mA

Answer 14

0.001 A

Question 15

What is the rule for current in a series circult

Answer 15

I1 = I2 = I3

Question 16

What are charge carriers

Answer 16

the delocalised electrons moving though wires or ions, moving through electrolytes

Question 17

What is mean drift velocity - v

Answer 17

the average velocity of charge carriers as they move through a conductor (unit: ms-1)

Question 18

What equaltion for current links area, number density, electrons and mean drift velocity

Answer 18

I = Anev

Question 19

What is number density - n

Answer 19

the number of charge carriers per cubic meter pf a material (unit: m-3)

Question 20

What is voltage

Answer 20

the amount of electrical energy transfer per coulomb of charge (joules per second)

Question 21

What is EMF

Answer 21

-electromotive force
-the number of joules per unit charge to electrical energy
-eg/ cell, solar panel

Question 22

What does emf transfer

Answer 22

-the amount of energy per coulomb of charge transferreed from other forms into electrical
-energy transferred from other forms (eg/ light, chemical) to electrical energy PER UNIT CHARGE

Question 23

What does potential difference transfer

Answer 23

-the amount og energy per coulomb of charge transferred from electrical into other forms
-energy transferred from electrical to other forms (blub - light, heat or motor - kinetic) PER UNIT CHARGE

Question 24

What does the sum of emf =

Answer 24

sum of p.d

Question 25

Equation: Voltage =

Answer 25

E(energy transferred)/Q(charge) or W(work done)/Q(charge) energy transferred (J) = work done (J)

Question 26

Describe the IV graph for wire at a constant temp

Answer 26

For a wire at a CONSTANT TEMPERATURE, as the potential differnce increases the curretn also increases, there fore the relationship is directly propertional = ohm's law

Question 27

Describe the IV graph for a filament lamp

Answer 27

As the voltage increases, temperature increases. As temperature increases, particles (metal ions), have more kinetic energy - if metal ions vibrate faster, there are more frequent collisions between the metal ions and electrons making it harder for the current to flow --> higher resistance. No direct proportion between voltage and current

Question 28

What is ohm' law?

Answer 28

'For a metallic conductor kept at a constat temperature, the current in the wire is directly proportional to the p.d across the ends'. Ohm's law does not apply to all components, so we can categoorise them as ohmic and non-ohmic conductors V = IR

Question 29

What will the graph of an ohmic conductor look like?

Answer 29

a straight line through the origin

Question 30

Describe the IV graph for a Diode

Answer 30

Diodes are non-ohmic. The diode only allows current tot flow in one direction (forward direction), the diode has a high resistance in the opposite direction (reverse direction) It needs a certain p.d to be able to conduct. This is known as the threshold p.d - when the trapped orbitting electrons gain enough force to become delocalised - which then gradually decreases the resistance. Before the threshold p.d there is a very low number density - meaning the number of charge carriers per unit volume is very low, which means low/no current. (and there is a very high resistance)

Question 31

Describe the graph for a thermistor

Answer 31

For a thermistor, as the temperature increases, the resistance decreases at a decreasing rate. If the resistance is decreasing it is therefore easier for electrons to flow which increases the current

Question 32

Describe the graph for a LDR

Answer 32

For an LDR, as thelight intensity increases, the resistance decreases at a decreasing rate

Question 33

What is resistance

Answer 33

how difficult it is for electrons to flow through a component

Question 34

What is the equation for work done

Answer 34

W = Q(charge) x V(voltage)

Question 35

What is the equation for power - rate of energy transfer

Answer 35

power (w) = energy (j)/time (s) or power (w) = p.d (v) x current (a) or power (w) = I squared x R or power = V squared / R

Question 36

What is Kirchoff's second law

Answer 36

The sum of the emfs in any loop in a circuit is equal to the sum of the pds around that loop (based upon the conservation of energy)

Question 37

What is the equation ot calculate potential dividers

Answer 37

V out = V in x R2/R1 + R2

Question 38

What is the equation for resistors in series?

Answer 38

RT = R1 + R2...

Question 39

What is the equation for resistors in parallel?

Answer 39

1/RT = 1/R1 + 1/R2

Question 40

Define electrical resistance

Answer 40

Resistance = potential differnce/current

Question 41

What is the equation for net charge

Answer 41

Net charge (Q) = no. Of electrons x 1.6x10-19