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CLASS X
Physics
Electricity
Part-1
# Electric charge. :- Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field.

# Types of electric charge :- Electric charges are of two types -
1) Positive charge (proton)
2) Negative charge (electron)

# Property of charges -

1) opposite charges attract each other
2) similar charges repel each other.

# The SI unit of electric charge is coulomb (C).

#. A proton possesses a positive charge of
+1.6*10^-19.

# An electron possesses a negative charge of -1.6×10^-19.

# 1 coulomb charge contains 6.25×10^18 electrons.

# Electric Potential - The electric potential at a point in an electric field is defined as the work done in moving a unit positive charge from infinity to that point.

# Potential difference - The potential difference between two points in an electric circuit is defined as the amount of work done in moving a unit charge from one point to another point.
V= W/Q
Where W=work done
Q=quantity of charge
# The SI unit of potential difference is volt.

# 1volt. :- The potential difference between two points is said to be 1 volt if 1joule of work is done in moving one coulomb of electric charge from one point to another.

# Voltmeter - A device which is used to measure potential difference is called voltmeter.

# Voltmeter is connected in parallel in a circuit because of having high resistance so that it takes a negligible current.

# It is the potential difference between the ends of the wire which make the electric charges to flow in the wire.

# Current :- The continuous flow of electric charges through a conductor per unit time.
I =Q/t
# SI unit of current is ampere (A) .

# 1 ampere :- When one coulomb of charge flows through any cross section of a conductor in 1 second the electric current flowing through it is said to be one ampere .

# Direction of current. :- The direction of current is just opposite to the direction of flow of electrons.

# Ammeter - A device which is used to measure current is called ammeter.

# Ammetre is connected in series in a circuit because of having very low resistance so that it may not change the value of the current flowing in the circuit.

# Resistance :- The property of a conductor due to which it opposes the flow of current through it is called resistance.
R = V/I
# SI unit of resistance is ohm.

# 1ohm :- 1 ohm is the resistance of a conductor such that when a potential difference of 1 volt is applied to its ends a current of 1 ampere flows through it.

# Factors affecting the resistance of a conductor -

1) Length of the conductor - The resistance of a conductor is directly proportional to its length.

2) Area of cross section of the conductor - The resistance of a conductor is inversely proportional to its area of cross section.

3) Temperature - The resistance of the conductor is directly proportional to the temperature.

4) Nature of the conductor - The resistance
of the conductor is depends on the nature of the material.

# Resistivity - The resistivity of a substance is numerically equal to the resistance of the rod of that substance which is one metre long and one square metre in cross section.

# The SI unit of resistivity is ohm-metre.
# The resistivity of a substance does not depend on its length or thickness.

# The resistivity of a substance depends on the nature of the substance and temperature only.

# The resistivity of the the conductor increases on increasing temperature.

# The resistivity of insulators are not affected by temperature.

# The resistivity of semi conductors decreases on increasing temperature.

# Nichrome is used for making the heating elements of electrical appliances such as electric iron, toaster ,electric kettle, room heater ,water heater and hair dryer because nichrome has very high resistivity and and does not undergo oxidation easily when at high temperature.

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