Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Basics > Electric current > Flashcards

Electric current Flashcards

1
Q

Electric current

A

The collective motion of particles carrying electric charge. Requires the relatively free motion of charge carriers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Conductor

A

a material that contains charge carriers which can move freely

e.g: metals due to free electron cloud resulting from the metallic bond, and electrolyte solutions due to freely moving ions in liquid phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Insulator

A

When there is no freely moving charge carriers in the material.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

DC - direct current

A

Is constant in time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

AC - alternating current

A

changes as a sine function over time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Direction of current

A

Defined according to the flow direction of positive charges (conventional current direction). Electrons in metals moves in opposite direction due to their negative charge.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Electric current

A

amount of charge passing through a given cross section in a unit of time

I = Δq/Δt

unit: ampere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Speed of motion of electric charges is dependent on

A

resistance exerted by conducting material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Ohms law

A

U = R*I

R does not depend on voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Law of resistance

A

R = U/I

Unit: Ohm

Ohmic resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Resistance of a conductor depends on..

A

Its dimensions and material properties.

Long conductor - weaker electric field, motion of charges is slower, lower electric current - greater resistance

Greater cross sectional area - more charge carriers can pass for a given voltage and electric field strength

R = specific resistance* (l/A)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Electric conductance

A

G = 1/R

Unit: S, Siemens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Specific conductance or conductivity

A

δ = 1/ρ

Unit: S/m

Is directly proportional to ion concentration within certain limits.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Connecting resistors:

A

Series: R= r1+r2+r3+…
Parallel: 1/R = 1/R+1/R+1/R+…

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Joule heating

A

or work of the electric current

the work done by the electric field when moving electric charge carriers which turns into another form of energy; in case of ohmic resistors it turns completely into thermal energy (heat)

W = UIt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Electric power

A

electric work done in unit of time
P=U*I

Unit: Watt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Electrical circuit

A

An interconnection of electrical components enabling electric current flow.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Kirchhoff’s current law/first law/junction law

A

as a result of conservation of electric charge, the currents flowing into a junction are equal to the currents flowing out of that junction -> in a branched circuit, current is partitioned between the branches.

19
Q

Kirchhoff’s voltage law/loop law/ second law

A

As a result of conservation of energy, the directed sum of voltages of electrical components along a loop within an electrical circuit is zero. In a branched circuit, voltage is partitioned between the electrical components.

( increase in capacitor voltage = decrease in resistor voltage)

When voltage of capacitor is equal to the battery voltage, and we remove the battery, the voltage of the capacitor and the voltage of the resistor is equal but with opposite signs.

20
Q

RC circuit

A

An electrical circuit consisting of an ohmic resistor and a capacitor. In order to charge a capacitor we will need to connect a voltage source (battery). In order to discharge the capacitor, we have to remove the battery and connect the two poles of the capacitor through the resistor.

21
Q

Battery voltage is approached…

A

asymptotically by capacitor voltage

Resistor voltage decreases as capacitor voltage increases
Current decreases as resistor voltage decreases ( Ohm)
Charging is complete when current and resistor voltage is zero.

After charging: insulator between the plates of the capacitor -> the capacitor presents an infinite resistance in a DC circuit

22
Q

Function for capacitor charging

A

Uc=Ub(1-e^(-t/RC))

Uc is voltage of capacitor at time t (s)
Ub is battery voltage
R is resistance
C is capacitance

RC = time constant of the RC circuit

23
Q

Insulator between plates of the capacitor

A

The capacitor presents an infinite resistance in a DC circuit

24
Q

During discharging, current flows from…

A

higher potential (positive plate) to the lower potential (negative plate)

25
Q

Function for capacitor discharging

A

Uc=Uo*e^(-t/RC)

RC= time constant of the RC circuit.

26
Q

Alternating current circuit, current function and voltage function

A

Current and voltage changes periodically following a sine function

I= Imax*sinωt

U= Umaxsin(ωt+phase)

If the circuit contains only Ohmic resistors, there are no phase shifts.

27
Q

RMS/root-mean-square values

A

Effective values in case of sinusoidal AC

Ieff= Imax/square2

Ueff= Umax/square2

28
Q

Capacitor in an AC circuit

A

presents a finite “resistance” called capacitive reactance., current is maintained: the alternating current keeps continuously charging and discharging the capacitor with alternating electric polarity
Capatitive reactance:
Xc= 1/(ω*C)

high frequency AC has a negligible capacitive reactance

29
Q

Impedance

A

If an AC circuit contains both resistors and capacitors and the total “resistance” of the whole circuit is called impedance.

symbol: Z

U and I has to be considered as vectors perpendicular to each other. The impedance is the hypotenuse, with U and I as adjacent.

30
Q

Impedance in series and parallel

A

Series: R^2 + (Xc)^2 = Z^2
Parallel: (1/R)^2 + (1/Xc)^2 =(1/Z)^2

31
Q

Electrodes

A

The metallic parts in direct connection with a non-metallic component.

Metals where the charge carriers are the mobile electrons in connection with non-metallic components like solutions, tissues, body parts, vacuum etc.

32
Q

What is the non metallic component of a Galvanic cell/Electrolytic cell/pH meter?

A

Electrolyte solution

33
Q

What is the non metallic component of an ECG defibrillator?

A

The body around the heart

34
Q

What is the non metallic component of an EEG?

A

The head

35
Q

What is the non metallic component of micro electrodes?

A

The interior or the exterior of a cell

36
Q

What is the non metallic component of an ultrasound generator?

A

Piezoelectric crystal

37
Q

What is the non metallic component of gas discharge lamps?

A

metal, vapor or gas

38
Q

What is the non metallic component of a vacuum tube?

Cathode ray tube, X-ray tube of photomultiplier tube

A

Vacuum

39
Q

What is the non metallic component of semiconductor devices?

diode, transistor, integrated circuit

A

Semiconducting crystal

40
Q

Anode

A

The electrode that attracts anions(negatively charged ions) from the non-metallic component

41
Q

Cathode

A

The electrode that attracts cations (positively charged ions) from the metallic component

42
Q

(PP) What is the resistance of a 100 m long steel cable it its cross section is 5cm^2?

A) 0,02 Ohm
B) 2 Ohm
C) 500 fOhm
D) 2 microOhm

A

R= specific resistance* l/A

A

43
Q

(PP) A 20 kOhm resistor is connected to a 100 V voltage source. Which of the following statements is correct?

A) The electric power is 2 MW

B) The electric power is 0,5 W

C) The current flowing though it is 200 A

D) The current flowing through it is 5 A

A

A

Basics (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions