electrical circuits

Question 1

charge

Answer 1

a quantity that some particles have ( +/- ) (Q) AT (coulomb)

Question 2

current

Answer 2

the rate of flow of charge (i) ( amps A ) Q/T

Question 3

potential difference

Answer 3

Energy transfer between two points of a circuit per unit charge (across or over) (v) (voltage) W/Q

Question 4

resistance

Answer 4

ability to oppose the flow of current ( ohm) V/I

Question 5

Emf (electromotive force)

Answer 5

what batteries supply ( push of current) ( energy transferred to the circuit per unit charge) ( voltage)

Question 6

Kirchhoff’s Current Law (KCL):

Answer 6

sum of currents entering a junction equals the sum of currents leaving it.

Question 7

kirchhoffs pd law

Answer 7

The sum of voltage rises equals the sum of voltage drops in a closed loop.

Question 8

power

Answer 8

The rate at which electrical energy is transferred by an electric circuit, measured in watts (W).

Question 9

Resistor

Answer 9

A passive two-terminal electrical component that resists the flow of current, dissipating energy as heat.

Question 10

Diode

Answer 10

A semiconductor device that allows current to flow in one direction only, blocking reverse current flow.

Question 11

Ohm’s Law

Answer 11

The fundamental relationship between voltage, current, and resistance:
V=IR.

Question 12

resistivity

Answer 12

Resistivity is a fundamental property that describes how much a material opposes the flow of electric current through it.
It is specific to each material and depends on temperature.
The unit of resistivity is ohm meters (Ω m).

Question 13

resistivity conditions

Answer 13

The longer the wire, the greater its resistance.
The thicker the wire (larger cross-sectional area), the smaller its resistance.
The resistivity equation shows that:
Resistance ((R)) is directly proportional to the length ((L)) of the wire.
Resistance ((R)) is inversely proportional to the cross-sectional area ((A)) of the wire.

Question 14

materials and resistvity

Answer 14

Materials with higher resistivity exhibit greater resistance.

Question 15

equation for resistivity

Answer 15

r = pI/A

Question 16

drift velocity

Answer 16

Drift velocity represents the average velocity of charge carriers (usually free electrons) as they move through a conductor.
These charge carriers experience frequent collisions with metal ions, limiting their overall speed.
The typical drift velocity for free electrons in conductors is approximately 10^(-3) m/s

Question 17

Understanding Drift Velocity

Answer 17

n a current-carrying conductor, the movement of charge carriers (electrons) contributes to the flow of electric current.
Despite their high density in conductors, free electrons travel only short distances before colliding with metal ions.
Consequently, their drift velocity remains relatively slow.

Question 18

drift velocity equation and meanings

Answer 18

The current ((I)) can be expressed using the transport equation: [ I = nqvA ] where:
(n) represents the number density (number of charge carriers per unit volume, usually electrons).
(q) is the charge of the charge carrier.
(v) denotes the drift velocity.
(A) is the cross-sectional area of the wire.

Question 19

Significance of Drift Velocity:

Answer 19

Drift velocity is crucial because it determines the overall current flow.
Materials with more charge carriers (higher (n)) exhibit greater current for the same applied voltage.
Insulators, with few charge carriers, have extremely high resistivity and negligible current flow.

Question 20

What is a Potential Divider?

Answer 20

A potential divider is a circuit arrangement commonly used to divide a voltage (potential difference) into smaller fractions.
It consists of two resistors (R₁ and R₂) connected in series.
The current flowing through both resistors is the same, as they are in series.

Question 21

Mathematical Expression

Answer 21

The potential across resistor R₁ is denoted as (V₁), and across resistor R₂ as (V₂).
According to Ohm’s law, the potential difference across a resistor is given by: [ V = IR ]
Applying this to our potential divider:
(V₁ = IR₁)
(V₂ = IR₂)

Question 22

what is the total pd divided in the circuit?

Answer 22

The total potential difference ((V)) is divided between the two resistors based on their resistances: [ V = V₁ + V₂ ] [ V = IR₁ + IR₂ ] [ V = I(R₁ + R₂) ]

Question 23

Variable resistor uses

Answer 23

A variable resistor allows current control in a circuit.
It consists of a length of resistance wire with an adjustable sliding contact.
The resistance can be varied without switching off the circuit.
Used in car lighting systems to adjust brightness.

Question 24

potentiometer

Answer 24

Similar to a variable resistor but with all three points (both ends of the resistance wire and the adjustable contact) connected to the circuit.
The resistance increases as the wire length increases.
Used, for example, to change volume in speaker systems.

Question 25

resistance in series

Answer 25

r1 + r2 etc

Question 26

resistance in parallel

Answer 26

(1/r1+1/r2)^-1 Prove= conservation of charge vt= v1 = v2 and it = i1 + i2 etc. r= v/i so rt = v/i1+ v/i2 etc so rt = 1/r1 + 1/r2 etc

Question 27

How resistance of a thermistor changes as temperature decreases

Answer 27

as temperature decreases, the resistance of a thermistor will increase

Question 28

why the resistance of a thermistor will decrease with an increase of temperature

Answer 28

as temp increases, conduction electrons are liberated meaning there are more charge carriers and so current can flow more easily

Question 29

decribe how the resistance of a ldr changes as light intensity increase

Answer 29

as light increases, the resistance of a ldr will decrease