Some electrical components do not obey Ohm's Law, where voltage is directly proportional to current. These components are called semiconductors or non-ohmic devices. Semiconductors include filament bulbs, diodes, thermistors, and light dependent resistors (LDRs). Filament bulbs have resistance that increases with current, diodes only allow current to flow in one direction, thermistors have resistance inversely proportional to temperature, and LDRs have resistance inversely proportional to light intensity. These semiconductors can control when and how much current flows in a circuit.
3. What is the resistance of the wire? At the molecular level what is physically happening?
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7. (1) Filament Bulb Voltage Current In the bulb as the voltage goes up , so will the heat energy (vibrations of the atoms) and therefore the electrons find it difficult to flow. Resistance (shown by the gradient of the graph) is seen to increase as current increases Current is not proportional to voltage!
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9. (2) Diode Current Voltage Ohm’s Law is clearly not obeyed as voltage is not directly proportional to current. The diode allows current to flow in one direction only – known as forward bias but only at a definite voltage (usually about 0.6V).
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