Dc and Ac Circuites

Question 1

Direct current

Answer 1

Comes out of battery
Magnitude stay constant over time
I=q/t

Question 2

Electromotive force (EMF)

Answer 2

E
(voltage) drives current
Emf source-battery
Allow charges to flow from one end to another

Question 3

Kitchhoff’s loop rule

Answer 3

sum of V across a closed circuit has to = sum of V gains across circuit
V drops across all of R in the circuit will = V gained by the battery
Conservation of E

Question 4

Resistance of conductor

Answer 4

R
Measure of particular conductor’s resistance to current flow
R - device used to intentionally cause V drop in circuit

Question 5

Resistivity of material

Answer 5

Ro
Measure of its resistance to I flow
If material has higher resistivity, then applying given potential difference across it will produce lower I
Resistance of R depends on resistivity of material
R=ro*L/A, L- length of R, A- cross- sectional area through which I flow.

Question 6

Ohm’s law

Answer 6

V across R - proportional to I passing through it
V=I*R
R- proportionality constant
Units of R - ohm= 1 v/ a

Question 7

Resistors in series

Answer 7

When 2/> R in series, I has no choice but to pass through all of them.
R total or equivalent = R1+ R2…

Question 8

Resistors in parallel

Answer 8

When 2/> R in parallel configuration, C is split btwn different parts, V across each path - same.
1/Req=1/R1+1/R2….

Question 9

Internal resistance

Answer 9

R of battery
Contributes to R total
Usually = 0
When not 0, it will reduce effective potential of battery
When battery has internal r, terminal V of battery< battery EMF: V= emf - Ir
I= Emf/(R+r)

Question 10

Capacitor

Answer 10

Two conductors with V btwn them, in short distance apart, used to store electrical E.
When 2 in charged conductors are connected to opposite terminals of battery, equal amounts of + and - charge move to each of conductorsrs

Question 11

Capacitance

Answer 11

C
amount of charge that C can hold depends on C
C= Q/V
SI units Farad: 1 F= 1C/V

Question 12

E stored by capacitor

Answer 12

PE
When battery is hooked to uncharged C, it must do work in charging C.
electrical PE of C increases as W done on it
PE stored in fully charged C, U= 1/2CV^2

Question 13

Parallel plate capacitor

Answer 13

Consists of 2 flat conducting plates, with surface area A, separated by distance d.

Question 14

Capacitors in series

Answer 14

When 2/> in series, each C has to store same amount of charge
V=Q/Ceq
Each series C individually stores same amount of charge: V=V1+V2=Q/C1+Q/C2
1/Ceq=1/C1+1/C2

Question 15

Capacitors in parallel

Answer 15

V drops across C in parallel are same
Total charge stored divided btwn 2 C in parallel
Q=VC1+VC2=V(C1+C2)
Ceq=C1+C2

Question 16

Dielectric

Answer 16

Non-conducting material placed btwn plates of C
Air, rubber, glass, plastics
When inserted increase capacitance
Cnew=kCold, k - dielectric constant of material

Question 17

Alternating current

Answer 17

AC I and V periodically reverse direction, in US 60 times/ s
I is also vary sinusoidally in time
I=V/Req=Vmax/Req*sinwt

Question 18

Magnitude of AC voltage or current

Answer 18

Root-mean-square(rms)
Kind of average, in any particular moment of time value for them can be btwn 0 + maxvalue
Irms=Imax/root2
Vrms=Vmax/root2

Question 19

Electric power

Answer 19

P=IV, higher I or V, > E transferred over given amount of time
P=I^2R, higher R, faster E is dissipated
In AC circuit use rms value for I and V to calculate P.