(a) State Ohm's Law. Under what conditions is it true? Sketch the V-I grap for a material that obeys Ohm's Law.
(b) The resistance of a filament is 1.2 kΩ. If it needs a current of 0.20A to light up, what is the potential difference across the lamp when it is in use?
(c) Draw graphs p.d. V against the current I for the following materials:
(i) A filament lamp
(ii) A thermistor
(iii) A semiconductor diode
*************************
Answer:
(a) Ohm's Law states that the voltage across the ends of a conductor is directly proportional to the current flowing through it, provided that the temperature and other physical conditions are changed.
(b) potential difference = 1.2 k * 0.2 = 0.24 kV = 240 V
(c)
(i) Filament Lamp
(ii) Thermistor
(iii) Semiconductor Diode
