3. Conductors:
• Materials which allow electric current to flow
through them easily are called conductors.
• Every material is made up of atoms which are tiny
particles invisible to the human eye.
• Electron is one of the component of an atom.
• Electron of different types of atoms have different
degrees of freedom to move around.
• In a conductor, the outer-most electrons of the
atom are loosely bound and can freely move
through the material when an electric charge
applied.
• Thus electricity can pass through them.
4. • Metals in general are the best conductors of
electricity.
• The atoms of metal elements are characterized by
the presence of electrons in the outer shell of an
atom that are free to move about.
• It is these ‘free electrons’ that allow metals to
conduct electric current.
• Many metals like copper, iron, silver etc. are good
conductors of electricity.
• Silver is the most conductive metal, however it is
very expensive and hence is rarely used.
5. • It is an excellent conductor of electricity and
is affordable.
• All the electric wires are generally made from
copper.
• Even though carbon and graphite’s are non-
metals, they are good conductors of
electricity.
6. Insulators :
• Insulators are opposites of conductors.
• In insulators the outer electrons are tightly held
together, which prevents them from moving.
• When the movement of electrons is restricted, no
current can flow through them.
• Non-metals such as glass, wood, plastic are
excellent insulators as they have high resistance to
the flow of electric current.
• This is true for normal voltage but increase in
voltage may conduct some passage for electricity.
• Insulating materials like plastic, wood etc are used
to cove materials that carry electricity.
7. Superconductors:
• Though metals are good conductors of electricity
they are not perfect conductors.
• Some current is lost in the transfer as there is some
resistance to the flow of current.
• A superconductor is a materials that is a perfect
conductor.
• It has zero electrical resistance. Superconductors
are usually a mix of two or more metals.
• However these are not superconductors at room
temperature.
• They show zero resistance to electric flow at very
low temperature usually below -200o C.
8. Important facts:
• Like electricity heat can be conducted as well. Most
electrical conductors are also excellent conductors
of heat as well.
• Temperature plays a very important role in the
conductivity capabilities of a material.
• In general the higher the temperature the lower
the conductivity as resistance increase with
temperature and vice-versa.
• Aluminium is a cheaper option to make wires
compared to copper, however is not good
conductor as copper. This will save costs for wiring
however will increase consumption of electricity.
9. Conductors Fair conductors Good Insulators
Common conductors and insulators:
Silver Carbon Oil
Copper Human body Fur
Gold Moist human skin Silk
Aluminium Acid solution Wool
Magnesium Salt water Rubber
Tungsten Earth Glass
Nickel Water vapour (in air ) Plastic
Mercury ----- Wood
Platinum ----- Paper
Iron ----- Wax
10. • It must be noted that all conductive material do
not have the same conductivity and similarly not all
insulators have the same level of insulation.
• Conductivity and insulation also depends on
physical dimension of the material.
• Two wire of same length but with different
diameter, the wire with bigger diameter is a better
conductor then the wire with lesser diameter.
• Similarly two wires of same diameter but with
different lengths then the wire with shorter length
has proved to be a better conductors then the
longer wire.
11. • The electrical properties of some material differ under
different conditions.
• Most materials are poor conductors at high
temperatures and god conductors when cooled.
• Some of the materials are pure conductors at
extremely low temperatures which we call super
conductors.
• As the electrons in conductors are free to move, such
electrons can be forced to move in a direction.
• As electron move forward it pushes the electron in
front of it, which in turn pushes the electron in front of
it and all such electrons move forward in a group.
• This is what we call electric current or electricity.
• The path thus decided is what we call electric circuit.
13. 1) ____ allows most electricity to pass through them.
a) Insulators
b) Conductors
c) Semi-conductors
d) None of these
2) ________ move freely in conductors which allow
flow of electricity.
a) Atoms
b) Protons
c) Current
d) Electrons
b) Conductors
d) Electrons
14. 3) _______ metal is a bad conductors of Heat
a) Steel
b) Aluminium
c) Mercury
d) Wood
4) _______ has zero resistance.
a) Super-conductors
b) Water
c) Ice
d) Silver
5) ______ allows some electricity to pass through them.
a) Insulators
b) Conductors
c) Semi-conductors
d) None of these
c) Mercury
a) Super-conductors
c) Semi-conductors
15. 6) Super conductors work only at temperature below
______
a) -200o F b) 200o C
c) 200o F d) -200o C
7) Electrons are stable in __________.
a) Insulators b) conductors
c) Semi – conductors d) none of these
8) _______ does not allow electricity to pass through
them.
a) Water b) silicon
c) Graphite d) Plastic
d) -200o C
a) Insulators
d) Plastic
16. 9) ______ does not allow electricity to pass through
them.
a) Insulators b) conductors
c) semi-conductors d) none
10) _______ is a non-metal though a good conductor
of electricity.
a) Steam b) wax
c) Carbon d) rexene
11) When temperature increases, registance _______
a) Increases b) decreases
c) Remains same d) none
a) Insulators
c) Carbon
a) Increases
17. 12) ______ are used in mobile phones.
a) Conductors b) insulators
c) Semiconductors d) superconductors
13) _______ is a perfect conductors.
a) insulators b) semiconductors
c) Superconductors d) none
14) ________ behave in between the conductors and
insulators.
a) Aluminium b) copper
c) Gallium d) semiconductors
c) Semiconductors
c) Superconductors
d) semiconductors
18. 15) _______ are usually a mixture of two or more
metals.
a) superconductors b) conductors
c) Insulators d) semiconductors
16) Aluminium is cheaper than silver.
a) True b) false
17) Aluminium is a better conductor of electricity
compared to copper.
a) True b) false
a) superconductors
a) True
b) false
19. 18) Silver is the best conductor of electricity
compared to others.
a) True b) false
19) Pure water conducts electricity.
a) True b) false
20) Electrons are the only part of any atom.
a) True b) false
a) True
b) false
b) false
