Class notes Science

PHYSICS IMPORTANT TOPICS

1.State the ohm’s law , joule’s law , right hand thumb rule and left hand rule .

Ans :

a) OHM’S LAW :

The flow of electric current is directly proportional to the potential difference in a
conductor at constant temperature .

V=IR

b) JOULE’S LAW :

1. Heat produce in a resistor is directly proportional to the square of the current .

2. Heat produce in a resistor is directly proportional to the resistance for the current
flow.

3. Heat produce in a resistor is directly proportional to the time taken .

H = I2Rt


c) RIGHT HAND THUMB RULE :


Imagine you are holding a current carrying conductor in your right hand, the thumb

indicates the direction of the current and the enclosed fingers indicates magnetic field

lines.

, d) FLEMING’S LEFT HAND RULE :


Arrange the left hand fingers perpendicular to each other , the thumb indicates the

motion ( force ) of the conductor , the fore finger ( index finger ) indicates the magnetic

field lines and the middle finger indicates the direction of the current .




2.Write the SI units of current , potential difference , resistance , resistivity , power

and power of the lens .


Ans : a) Ampere(A) = Current = Is measured using = Ammeter .


b) Volts (V) = Potential difference and electric power = Voltmeter


c)Ohm = Resistance


d) Ohm – meter = Resistivity


e) Watt (W) = Power


f) Diopter (D) = Power of the lens .