sensing

Question 1

what is the definition for current?

Answer 1

current is the rate of flow of charge (units: amps, A)

Question 2

what is an equation for current?

Answer 2

an equation for current is:

I = ΔQ / Δt

Question 3

what is an equation for ΔQ (change in charge)?

Answer 3

an equation for ΔQ is:

ΔQ = Nq

where:
• N is the total number of charged particles
• q is the charge on one particle

Question 4

what is 1 coulomb?

Answer 4

1 coulomb is the charge flowing through a point in one second when there is a current of 1A

units for charge: Coulomb, C

Question 5

what is the definition of potential difference?

Answer 5

potential difference is the energy transferred per unit charge when moving between two points in a circuit

units: Volt, V

Question 6

what is an equation for pd?

Answer 6

an equation for pd is:

V = ΔE / Q
or
V = W / Q

where:
• W is work done between two points (units: Joules, J)

pd == voltage
energy transfer == work done

Question 7

what a an equation for work done?

Answer 7

an equation for work done is:

W = VIt

to help remember W = ItV (like ITV the tv channel)

Question 8

what is resistance?

Answer 8

resistance is the measure of the difficulty of passing an electric current through a medium

units: Ohms, Ω

Question 9

what are some equations for resistance?

Answer 9

some equations for R:

R = V / I
or
R = 1 / G

Question 10

equations for resistance concerning resistors in circuit?

Answer 10

resistors in series:
R tot = R1 + R2 + R3 + …

resistors in parallel:
R tot = 1/R1 + 1/R2 + 1/R3 + …

Question 11

what is conductance?

Answer 11

conductance is the measure of the ease of passing an electric current through a medium (so the opposite of resistance)

units: siemens, S

Question 12

equations for conductance concerning conductors in circuit?

Answer 12

conductors in series:
G tot = 1/G1 + 1/G2 + 1/G3 + …

conductors in parallel:
G tot = G1 + G2 + G3 + …

Question 13

what are some equations for conductance?

Answer 13

some equations for conductance are:

G = I / V
or
G = 1 / R

V = IR

Question 14

what is Ohm’s law?

Answer 14

⋅ Ohm’s law states that the voltage across a component is proportional to the current through it, ⋅ V = IR

Question 15

what is heat dissipation?

Answer 15

⋅ heat dissipation is the thermal energy transfer per second resulting in an increase in energy of the surroundings
⋅ heat dissipation is measured in watts, W

Question 16

how does heat dissipation occur?

Answer 16

⋅ heat dissipation occurs when:
1) electrons are accelerated by a pd, their movement is obstructed by the metal cations in the wire
2) the potential energy lost does work on the wire, heating it up

equation for heat dissipation:

Question 17

what is the relationship between heat dissipation-R and heat dissipation-G

Answer 17

⋅ heat dissipation increases with increased R, TE transfer ∝ R
⋅ heat dissipation decreases with increased G, TE transfer ∝ 1/G

Question 18

features of parallel circuits?

Answer 18

some features of parallel circuits are:
⋅ same pd [/ V] all around the circuit
⋅ different I around the circuit, split over each branch in inverse proportion to R (R1:I1 = R2:I2)
⋅(for multiple components on branches, add the resistances in series for each branch and then add the total resistance of each branch in parallel) (total R of parallel circuit always > lowest individual R)

Question 19

features of series circuits?

Answer 19

some features of series circuits are:
⋅ different pd, split over each component in proportion to R (V1:R1 = V2:R2)
⋅same I all around the circuit

Question 20

what is Kirchhoff’s First Law?

Answer 20

⋅ Kirchhoff’s First Law states that ‘the sum of the current entering an electrical junction equals the sum of the current leaving the junction’
⋅ Iin = Iout

Question 21

what is Kirchhoff’s first law based on?

Answer 21

⋅ Kirchhoff’s first law is based on the conservation of charge

Question 22

what is Kirchhoff’s Second Law?

Answer 22

⋅ Kirchhoff’s Second Law states that ‘the sum of all the potential differences and emfs across all of the components in a closed loop must be equal to zero’
⋅ PDtotal + EMFtotal = 0

Question 23

what is Kirchhoff’s second law based on?

Answer 23

⋅ Kirchhoff’s second law is based on the conservation of energy.

Question 24

what does Kirchoff’s law then also mean? (given that PDtotal + EMFtotal = 0)

Answer 24

⋅ given that PDtotal + EMFtotal = 0, Kirchhoff’s second law then also means that
EMFtotal = -PDtotal
⋅ (negative PDtotal bc voltage drops across circuit)

Question 25

what side is the negative terminal?

Answer 25

⋅ the short and bold side is the negative terminal

Question 26

what side is the positive terminal?

Answer 26

⋅ the long and thin side is the positive terminal

Question 27

what does the I-V graph for an ohmic resistor look like?

Answer 27

⋅ the I-V graph for an ohmic resistor is a proportional, linear line through the origin

Question 28

what does the I-V graph for a filament lamp look like?