PHYSICS PROJECT

Electronic symbols and ohm’s law

INDEX Electronic symbols

Ohm’s law

ELECTRONIC SYMBOLS

An electronic symbol is a pictogram used to represent various electrical and electronic devices (such as wires, batteries, resistors, and transistors) in a schematic diagram of an electrical or electronic circuit. Circuit symbols are used in circuit diagrams which show how a circuit is connected together.The actual layout of the components is usually quite different from the circuit diagram.

SOME OF THE MOST COMMONLY USED COMPONENTS IN CIRCUIT DIAGRAMS

Wire Symbol:

Function: To pass current very easily from one part of a circuit to another

Wires joined

Symbol:

Function: A 'blob' should be drawn where wires are connected (joined), but it is sometimes omitted. Wires connected at 'crossroads' should be staggered slightly to form two T-junctions, as shown

Wires not joinedSymbol:

Function: In complex diagrams it is often necessary to draw wires crossing even though they are not connected.

CellSymbol:

Function: Supplies electrical energy. A single cell is often wrongly called a battery, but strictly a battery is two or more cells joined together.

Battery

Symbol:

Function: Supplies electrical energy. A battery is more than one cell.

Fuse

Symbol:

Function: A safety device which will 'blow' (melt) if the current flowing through it exceeds a specified value.

Lamp (lighting)

Symbol:

Function: A transducer which converts electrical energy to light. This symbol is used for a lamp providing illumination, for example a car headlamp or torch bulb.

On-Off Switch

Symbol:

Function: An on-off switch allows current to flow only when it is in the closed (on) position.

Resistor

Symbol:

Function: A resistor restricts the flow of current, for example to limit the current passing through an LED. A resistor is used with a capacitor in a timing circuit.

Variable Resistor (Rheostat)

Symbol:

Function: This type of variable resistor with 2 contacts (a rheostat) is usually used to control current. Examples include: adjusting lamp brightness, adjusting motor speed, and adjusting the rate of flow of charge into a capacitor in a timing circuit.

Voltmeter

Symbol:

Function: A voltmeter is used to measure voltage or potential difference.

Ammeter

Symbol:

Function: An ammeter is used to measure current.

Galvanometer

Symbol:

Function: A galvanometer is a very sensitive meter which is used to measure tiny currents, usually 1mA or less.

OHM’S LAW

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 = RIWhere R is a constant of proportionality called resistance of the resistor, it tends to resist the flow of charge through a conducting wire. Its SI unit is Ohm (Ω).

Thus, we can write Ohm’s law as The law was named after the German physicist Georg Ohm, who, in a treatise published in 1827, described measurements of applied voltage and current through simple electrical circuits containing various lengths of wire. He presented a slightly more complex equation than the one above to explain his experimental results. The above equation is the modern form of Ohm's law.

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 difference the same), current will reduce to half.

The material that follows Ohm’s law is known as an ohmic material.

The material that does not follow Ohm’s law is known as a non-ohmic material.

THANK YOUMADE BY- ANUSHKA NINAMA

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