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# Physics

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### Physics

1. 1. Electronic symbols and ohm’s law
2. 2. An electronic symbol is a pictogram used to represent various electrical and electr onic devices (such as wires, batteries, resistors, and transistors) in a schematic diagram of an electrical or electronic circuit. Circuit symbols are
3. 3. A 'blob' should be drawn where wires are connected (joined), but it is sometimes omitted. Wires connected at 'crossroads'
4. 4. In complex diagrams it is often necessary to draw wires crossing even though they are not connected.
5. 5. Supplies electrical energy. A single cell is often wrongly called a battery, but strictly a
6. 6. Supplies electrical energy. A battery is more than one cell.
7. 7. A safety device which will 'blow' (melt) if the current flowing through it exceeds a
8. 8. A transducer which converts electrical energy to light. This symbol is used for a lamp providing illumination, for example a car headlamp
9. 9. An on-off switch allows current to flow only when it is in the closed (on) position.
10. 10. A resistor restricts the flow of current, for example to limit the current passing through an LED. A resistor
11. 11. This type of variable resistor with 2 contacts (a rheostat) is usually used to control current. Examples include: adjusting lamp brightness,
12. 12. A voltmeter is used to measure voltage or potential difference.
13. 13. An ammeter is used to measure current.
14. 14. A galvanometer is a very sensitive meter which is used to measure
15. 15. According to ohm’s law, under constant physical condition i.e. constant temperature, pressure etc. the applied potential difference is directly proportional to the current flowing in the circuit. Or, V = RI Where R is a constant of
16. 16.
17. 17. hence, according to ohm’s law, current is Directly proportional to potential difference. Inversely proportional to resistance. If the potential difference is doubled (keeping resistance the same), current will also get doubled. On the other hand, if resistance is doubled (keeping potential