Electric Current

Question 1

What is the formula for current density,j

Answer 1

I/A=qnvd

Question 2

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

Answer 2

πd²/4

Question 3

State ohms law

Answer 3

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

Question 4

Formula for resistivity

Answer 4

P=R A/L

Question 5

Examples of ohmic conductors

Answer 5

Eureka wires and carbon resistors

Question 6

Examples of non ohmic conductors

Answer 6

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

Question 7

Resistivity depends on

Answer 7

The material and temperature

Question 8

Unit of resistivity

Answer 8

Ohm meter

Question 9

Resistivity of ohmic materials are independent of

Answer 9

The magnitude E of the applied Force

Question 10

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

Answer 10

1.10

Question 11

What is superconductivity

Answer 11

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

Question 12

List the applications of superconductors

Answer 12

They’re used in manufacturing high field superconducting magnet

Used in cables for distributing power

Used in sensitive measuring instrument and in computer technology

Question 13

Positive electrode is called

Answer 13

Anode

Question 14

What is the potential difference between the terminals of a battery

Answer 14

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

Question 15

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

Answer 15

Lower

Question 16

Unit for current

Answer 16

Ampere

Coulomb per second

Question 17

Is current scalar or vector

Answer 17

Scalar

Question 18

Electron flow is from ______. Terminal to ________ terminal

Answer 18

Negative to positive

Question 19

Current in the wire is due to the flow of ________

Answer 19

Positive charges from positive terminal to negative terminal

Question 20

Unit of qn

Answer 20

C/m³

Question 21

_______ has the lowest resistivity

Answer 21

Silver

Question 22

_______ is another form of ohm’s law

Answer 22

J=ōE

Question 23

Is electric potential scalar or vector

Answer 23

Scalar

Question 24

The energy stored by a capacitor is equal to

Answer 24

The work done in charging the capacitor

Question 25

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

Answer 25

V∆q

Question 26

Moving the plates of a capacitor closer together will_______

Answer 26

Increase the capacitance

Question 27

What is the significance of loop rule

Answer 27

Conservation of energy

Question 28

What is the significance of junction rule

Answer 28

Conservation of charge

Question 29

When a glass rod is rubbed with silk what will happen

Answer 29

Electrons are removed from the rod

Question 30

Is electric current scalar or vector

Answer 30

Scalar

Question 31

What do you mean by varying current

Answer 31

A current whose magnitude changes with time

Question 32

What occurs when 2 charges are moved closer together

Answer 32

The Force between the charges increases

Question 33

Electric field strength depends on _________

Answer 33

Charge and distance

Question 34

What is the SI unit of current density

Answer 34

Ampere/ meter ²

Question 35

Is current density scalar or vector

Answer 35

Vector

Question 36

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

Answer 36

Zero

Question 37

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______

Answer 37

Two in series and the third in parallel across this combination

Question 38

Is electric field intensity scalar or vector

Answer 38

Vector

Question 39

The capacitor prefered for high frequency circuit is

Answer 39

Mica capacitor

Question 40

What is used to measure the unknown emf of a cell

Answer 40

Potentiometer

Question 41

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

Answer 41

Gauss law

Question 42

State Kirchhoff's junction rule

Answer 42

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

Question 43

State Kirchhoff's loop rule

Answer 43

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

Question 44

Ammeter is used to measure ____?

Answer 44

Current

Question 45

_______ is a high resistance instrument

Answer 45

Voltmeter

Question 46

_______ has a low resistance

Answer 46

Ammeter

Question 47

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

Answer 47

Multi meter