Chapter 6: Circuits

Question 1

conductance unit

Answer 1

siemens (S)

Question 2

conductivity unit

Answer 2

S /m

Question 3

current

Answer 3

I = Q / Δt

unit is ampere (1 A = 1 C /s)

Question 4

what are the two types of conductivity?

Answer 4

metallic conductivity and electrolytic conductivity

Question 4

electromotive force (emf)

Answer 4

when no charge is moving between the two terminals of a cell that are at different potential values

unit is volts

Question 4

Kirchhoff’s junction rule

Answer 4

I into junction = I leaving junction

At any point junction in the circuit, the sum of currents directed into that point equals the sum of currents directed away from that point.

Question 5

Kirchhoff’s Loop Rule

Answer 5

V source = V drop

The sum of voltage sources will always be equal to the sum of voltage drops. All the electrical energy supplied by a source gets fully used up by the other elements within the loop.

Question 6

resistors equation

Answer 6

R = ρL / A

ρ = resistivity
L = lenght of the resistor
A = cross sectional area

Question 7

what affects a resistor?

Answer 7

lenght, resistivity, temperature and cross sectional are

Question 8

resistivity (ρ)

Answer 8

unit is ohm -meter = Ω .m

Question 8

Ohm’s Law

Answer 8

V = IR

V = voltage drops
I = current
R = magnitude of the resistance , measured in ohms

Question 9

actual voltage supplied by a cell is

Answer 9

V = Ecell - irint

V = volatge provided by a cell
Ecell = emf of that cell
i = current throught that cell
rint = internal resistance

Question 10

power

Answer 10

P = W / t = ΔE / t

P = IV = I^2R = V^2/ R

Question 11

resistors in series

Answer 11

All current must pass sequentially through each resistor connected in a linear arrangement.

Vs = V1 + V2 + V3 + …+ Vn

Rs = R1 + R2 + R3 + …+ Rn

Question 12

what to do when approachign circuit problems?

Answer 12

The first thing you need to find are the total circuit values: The total voltage, the total resistance and the total current. To find it to recurrent, first find the total resistance of the circuit.

Question 12

resistor in parallel

Answer 12

The current will divide to pass through resistor separately. If every resistor is parallel, then the voltage drop across each pathway alone must be equal to the voltage of the source. Electrons before the path of least resistance. The current will be the largest through the pathways with the lower resistance.

Vp = V1 = V2 = V3 = …= Vn

1 /Rp = 1/R1 + 1/R2 + 1/ R3 + … + 1/Rn

Question 13

capacitance equation

Answer 13

C = Q / V

Q = charge it collects
C = capacitance
V = potential difference (voltage)

Question 13

units for a capacitance

Answer 13

farad (1 F = 1 C /V)

usually given in microfarads (1μF = 1 x 10^-6 F)

Question 14

potentail energy stored in a capacitator

Answer 14

U = 1/2 C V^2

Question 14

uniform electric field

Answer 14

E = V / d

the direction of electriv field at any point between the plates is from the positive plae towards the negative plate

Question 15

dieletric material

Answer 15

it increases the capacitance by a factor called the dielectric constant (k)

Question 15

capacitance due to a dieelectric material

Answer 15

C’ = k C

C’ = new capacitance
C = original capacitance

Question 16

capacitors in series

Answer 16

1/ Cs = 1/C1 + 1/C2 + 1/C3 + ….+ 1/Cn

Cs decreases as more capacitors are added. The total voltage is the sum of the individual voltages.

Question 16

capacitors in parallel

Answer 16

Cp = C1 + C2 + C3 + … + Cn

Question 17

how does dieletric material impact capacitance? voltage? charge?

Answer 17

capacitance: always increase capacitance
voltage: if is isolated, voltage will decrese, if in a circuit voltage is constant
charge: if isolated, it will remain constant.If in a circuit it will increase

Question 18

how does adding or removing a capacitor change the total capacitance of a circuit with capacitors in series? in parallel?

Answer 18

series: adding it will decrease total capacitance
parallel: adding will increase capacitance

Question 18

isolated capacitors

Answer 18

disconnected from any circuit

Question 19

ammeters

Answer 19

used ot measure the current at some point within a circuit

Question 20

voltmeter

Answer 20

used to measure the volatge drop across two points in a circuit.

Question 20

ohnmeter

Answer 20

calculate resistance by knowing the ohnmeter voltage and the current created thought another point in the circuit.