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Physics 102 > Electric Current > Flashcards

Electric Current Flashcards

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1
Q

What is the formula for current density,j

A

I/A=qnvd

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2
Q

What is the formula for the Cross sectional area A of a wire

A

πd²/4

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3
Q

State ohms law

A

It states that the current passing through a metallic conductor is directly proportional to the potential difference across it if the temperature is constant.

I¥V

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4
Q

Formula for resistivity

A

P=R A/L

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5
Q

Examples of ohmic conductors

A

Eureka wires and carbon resistors

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6
Q

Examples of non ohmic conductors

A

Thermionic diodes, junction diodes, photo cells and dilute sulphuric acid

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7
Q

Resistivity depends on

A

The material and temperature

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8
Q

Unit of resistivity

A

Ohm meter

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9
Q

Resistivity of ohmic materials are independent of

A

The magnitude E of the applied Force

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10
Q

20mm length wire 1.50mm in diameter has a resistance of 2.5. what is the resistance of a 35m length wire of 3mm in diameter made if the same material

A

1.10

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11
Q

What is superconductivity

A

This Is when some materials have a resistivity of zero below a certain temperature called critical temperature

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12
Q

List the applications of superconductors

A

They’re used in manufacturing high field superconducting magnet

Used in cables for distributing power

Used in sensitive measuring instrument and in computer technology

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13
Q

Positive electrode is called

A

Anode

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14
Q

What is the potential difference between the terminals of a battery

A

It is when no charge is allowed to flow in an external circuit known as electromotive force of the battery

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15
Q

When charge flows in the external circuit, the potential difference between the terminals is ________ than the emf of the battery

A

Lower

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16
Q

Unit for current

A

Ampere

Coulomb per second

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17
Q

Is current scalar or vector

A

Scalar

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18
Q

Electron flow is from ______. Terminal to ________ terminal

A

Negative to positive

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19
Q

Current in the wire is due to the flow of ________

A

Positive charges from positive terminal to negative terminal

20
Q

Unit of qn

A

C/m³

21
Q

_______ has the lowest resistivity

A

Silver

22
Q

_______ is another form of ohm’s law

A

J=ōE

23
Q

Is electric potential scalar or vector

A

Scalar

24
Q

The energy stored by a capacitor is equal to

A

The work done in charging the capacitor

25
Q

The work done ∆w necessary for transfer of a charge ∆q is

A

V∆q

26
Q

Moving the plates of a capacitor closer together will_______

A

Increase the capacitance

27
Q

What is the significance of loop rule

A

Conservation of energy

28
Q

What is the significance of junction rule

A

Conservation of charge

29
Q

When a glass rod is rubbed with silk what will happen

A

Electrons are removed from the rod

30
Q

Is electric current scalar or vector

A

Scalar

31
Q

What do you mean by varying current

A

A current whose magnitude changes with time

32
Q

What occurs when 2 charges are moved closer together

A

The Force between the charges increases

33
Q

Electric field strength depends on _________

A

Charge and distance

34
Q

What is the SI unit of current density

A

Ampere/ meter ²

35
Q

Is current density scalar or vector

A

Vector

36
Q

What is the average velocity of Free electrons in a metal at room temperature

A

Zero

37
Q

Three capacitors with the capacitance of C each is given a resultant capacitance of 2/3c this result can be obtained by connecting them in______

A

Two in series and the third in parallel across this combination

38
Q

Is electric field intensity scalar or vector

A

Vector

39
Q

The capacitor prefered for high frequency circuit is

A

Mica capacitor

40
Q

What is used to measure the unknown emf of a cell

A

Potentiometer

41
Q

_______is used in evaluating field intensity at a point due to a symmetric charge distribution

A

Gauss law

42
Q

State Kirchhoff’s junction rule

A

It states that at any junction point, the sum of all the currents entering the junction must be equal to the sum of the currents leaving the junction

43
Q

State Kirchhoff’s loop rule

A

This states that the algebraic sum of the potential difference around Any closed path on the circuit must be zero

44
Q

Ammeter is used to measure ____?

A

Current

45
Q

_______ is a high resistance instrument

A

Voltmeter

46
Q

_______ has a low resistance

A

Ammeter

47
Q

_____is an instrument which is adapted for measuring current voltage and resistance

A

Multi meter

Physics 102 (1 decks)

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