Electricity Flashcards
Electric charge?
Property of matter to attract or repel other materials. SI unit is coulomb (C)
Charge of electron?
1.6 x 10^-19 C
Q = n x e
Conductors?
Allow electrons to pass through them, has free mobile electrons in outermost shell.
Insulators?
Don’t allow current to pass through them. Don’t have free mobile electrons.
Semiconductors?
Allow some amount of electricity to pass through them.
Electric curent?
Rate of flow of electric charge. Unit is Ampere.
I = Q/T
Define ampere.
Flow of one coulomb of charge per second.
1A = 1C/1 second.
Ammetre?
Measure electric current in a circuit.
Potential difference?
Work done in moving a unit of positive electric charge from one point to another. (Measured with voltmeter.)
Electric potential?
Work done in moving a unit of positive electric charge from infinity to a certain point in an electric field. SI unit = Volt (V)
V = W/Q
Define one volt.
1 volt = 1 joule/1 coulomb
Electric circuit?
Continuous and closed path of electric current is called an electric circuit.
State ohms law.
At constant temperature, current flowing through circuit is directly proportional to potential difference applied across ends to conductor.
V = I x R
Resistance?
Property of a conductor to resist flow of charges through it. SI unit is ‘ohm’ Ω
1 Ω = 1 volt/1 ampere.
Variable resistance?
A component used to regulate current without changing the voltage source.
Rheostat?
Device used to change resistance of a circuit.
Factors on which resistance of a circuit depends?
Crossectional area of wire
Length of wire
Nature of material of wire.
Why tungsten is used a filament in bulbs?
Because tungsten is an alloy and doesn’t burn easily at high temperatures. (High melting point) 3380 degree celsius.
Electrical resistivity/specific resistance?
Measure of resistance of conductor made of unit length and 1m crossectional area.
R = ρ L / A
Resistance in series?
In series, current remains constant and potential difference changes.
Rs = R1 + R2 + R3
Resistance in parallel?
Potential difference remains same but current changes.
1/Rp = 1/R1 + 1/R2 + 1/R3
Heating effect of electric current?
When an electric current passes through a conductor which acts as a resistance wire, the resisting nature of conductor results in rise in heat level of conductor with time. This phenomenon is known as heating effect of electric current.
H = I^2 x R x T
Joules law of heating?
Implies that heat produced in a resistor is:
Directly proportional to square of current for a given resistance.
Directly proportional to resistance for a given current.
Directly proportional to time for which current flows through a resistor.
Applications of heating effect of electric current?
Iron, toaster, oven, kettle are based on joules law of heating.
