**Category : **10th Class

**What makes the charge flow through the conductors? Is it that the chargeflow on their own through the conductors? **The answer to this question isno. The charge do not flow on their own through the conductors. The chargeflow through the conductors due to the difference of electric pressure which iscalled the potential difference. This difference of pressure may be generatedby a cell or a battery or any other sources. Thus, electric potential may bedefined as the amount of work done in taking a unit positive charge from infinityto a particular point.

Therefore, \[V=\frac{W}{Q},\]

**Where,**

**W** is the work done

**Q** is the total charge

**V** is the potential difference

The SI unit of potential difference is **volt** and is named after **Alessandro Volta and Italian Physicist**. One volt is defined as the potential difference between two points in a current carrying conductor, when one joule of work is done in moving a charge of one coulomb, from one point of another. It can be measured with the help of an instrument called **voltmeter** which is always connected in parallel across the points, between which the potential difference is to be measured.

**Potential Difference**

The potential difference between any two point may be defined as the amount of work done in taking a unit positive charge from one point to another; The SI unit of potential difference is Volt. The potential difference between any two point is said to be of one volt, if one joule of work is done in moving one coulomb of **electric charge **from one point to another.

**Electric Current**

When two charge bodies, at different potentials, are connected by a metal wire, the electric charge will flow from the body at higher potential to the one at lower potential. This flow of charges in the metal conductor will constitute the electric current through the conductor. Thus, the flow of electron through -the conductor is called the electric current. The SI unit of electric current is ampere. It is expressed as

\[I=\frac{Q}{t}\]

**One ampere current is defined as the current produced by the flow of onecoulomb of charges through a cross sectional area in one second**. It can be measure with the help of an instrument called** ammeter**. It is always connected in series with the circuit in which the current is to be measured.

**Ohm’s Law**

According to ohms law, **at constant temperature the current flowing through a conductor is directly proportional to the potential difference across its end**. It gives the relationship between the current and the potential difference.

If **I** is the current flowing through the conductor and V is the potential difference across its ends then according to Ohm's law:

\[I\,\alpha \,\,V\]

\[\Rightarrow \,\,\,V=IR\]

where, R is the constant of proportionality and is called resistance of the conductor. The value of resistance depends on the length of the wire, area of the cross section, temperature and on the nature of material.

R a I and R a —

\[R\,\,\alpha \,\,I\] and \[R\,\,\alpha \,\,\frac{1}{A}\]

From above equation we have,

\[R=\,\,\rho \frac{I}{A}\], where p is the resistivity of the conductor

Thus, **resistivity of the conductor is defined as the resistance of theconductor of length one meter and having unit area of cross section. Its SI unit is ohm meter**.

**Graph between V and I**

If we draw the graph between potential difference V and the current I, taking V on x axis and I on y axis, we obtain a graph of straight line dividing the first quadrant into two equal half, as two quantities are proportional to each other.

The ratio \[\frac{V}{I}\] is always a constants and is equal to the resistance of the conductor.

**The charge of electron is: **

(a) \[1.6\times {{10}^{-19}}C\]

(b) \[2.6\times {{10}^{-19}}C\]

(c)\[0.6\times {{10}^{-19}}C\]

(d)\[1.6\times {{10}^{-18}}C\]

(e) None of these

** **

**Answer (a)**

**Which one of the following will have static charges?**

(a) Electric Bulb

(b) Electric Heater

(c) Dry Cell

(d) Glass Rod rubbed with Silk

(e) None of these

** **

**Answer: (d)**

**Which one of the following is a graph which satisfies ohms laws?**

(a)

(b)

(c)

(d)

(e) None of these

**Answer : (c) **

**Which one of the following instrument is used for measuring electric current?**

(a)

(b)

(c)

(d) All of these

(e) None of these

**Answer: (c) **

**Which symbol represents rheostat?**

(a)

(b)

(c)

(d)

(e) None of these

**Answer: (b)**

*play_arrow*Introduction*play_arrow*Electric Potential*play_arrow*Combination of Resistance*play_arrow*Domestic Circuit*play_arrow*Electrical Power

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