Static and Current Electricity

Question 1

Symbol of charge

Answer 1

Q

Question 2

Unit of charge

Answer 2

Coulomb(C)

Question 3

Why does a positive charge occur

Answer 3

Shortage of electrons

Question 4

Why does a negative charge occur

Answer 4

Excess of electrons

Question 5

Methods of charging?

Answer 5

Friction, conduction, induction

Question 6

What is the law of conservation of charge

Answer 6

Electric charge can neither be created nor destroyed

Question 7

Law of electrostatics

Answer 7

Like charges repel, unlike charges attract

Question 8

What is Coulomb’s law

Answer 8

The force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of their distance apart

Question 9

Equation for Coulomb’s law

Answer 9

F=kq1q2/r^2

Question 10

What is an electric field

Answer 10

Region where an electric charge will experience a force

Question 11

Rule of field lines

Answer 11

• start perpendicular to the charged surface
• they go from + to -
• they never touch or cross
• the denser they are, the stronger the field is

Question 12

What is essential for current to flow

Answer 12

• power supply

* complete circuit

Question 13

What is current

Answer 13

A flow of ‘free electrons’

Question 14

Formal for current

Answer 14

I=Q/t

Question 15

Current unit

Answer 15

Amperes

Question 16

What is voltage or potential difference

Answer 16

The work done(or energy transferred) per unit charge across a component

Question 17

What is the equation for voltage

Answer 17

V=w/q=e/q

Question 18

What is emf

Answer 18

Electromotive force is he voltage provided by the power supply on open circuit
• work done per unit charge
•e=w/q

Question 19

Unit for resistance

Answer 19

Ohm(Omega)

Question 20

What is resistance

Answer 20

It is a measure of opposition to current flow

Question 21

What causes resistance in metals

Answer 21

Vibrating metal ions in the lattice hindering the flow of ‘free’ electrons

Question 22

Resistance formula

Answer 22

R=p(resistivity)l(length)/A(cross sectional area)

Question 23

What is ohms law

Answer 23

The current flowing in a conductor is directly proportional to the potential difference across its ends provided the temperature and other physical conditions remain constant

Question 24

Ohms law equation

Answer 24

V=IR

Question 25

Properties of series circuit

Answer 25

• current is the same at every point

* total voltage across a combination of components is the sum of the individual component voltages

Question 26

Properties of parallel circuits

Answer 26

Current splits up between branches in agreement with Kirchhoff’s law
•the voltage across components connected in parallel is the same

Question 27

How to calculate total resistance in the different circuits

Answer 27

• series:R=R1+R2+R3…..

* parallel:1/R=1/R1+1/R2+1/R3…..