Electric Current, Charge, Electric Circuit and Numerical (X CBSE Physics)

Various phenomena which are related to the presence and flow of electric charge come under electricity. Electric charge is a physical property of matter which causes the matter to experience a force when placed in an electromagnetic field. The flow of electric charge is called electric current. Resistance is an important property of matter and it explains the relative ease or difficulty by which electric current can pass through a matter. Ohm’s Law explains the relation between electric current and resistance. Resistances can be combined in two combinations, viz. series and parallel. Parallel combination is used for most of the purposes, while series combination is used for some special purposes. A brief introduction to the Electricity shown in following figure:

Electric Current: The flow of electric charge is known as electric current. Electric current is carried by moving electrons through a conductor. In an electric circuit, the electric current flow in the opposite direction of the flow of electron (–ve charge) conventionally. It flows from the +ve terminal of battery or cell to –ve terminal.

Charge: It is a very small particle present in an atom it can be either negative (electron) or positive (proton).

“Coulomb” is the SI unit of charge, represented by C.

Video Lecture on Charge an object by friction, rubbing or tribo (Hindi-Eng Practical demo just click the link ) 

ퟺ👉 : Charge an object by friction, rubbing or tribo (Hindi-Eng Practical demo)

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https://www.youtube.com/watch?v=SybhcPEgoSI&list=PLbCd_1frDqy6BaYzgyO7mgeVQuvNpTX4n 

Net charge (Q) or Total charge: 1C (one coulomb) Net charge is equivalent to the charge contained in nearly electrons 6X10¹⁸.

Expression of Electric Current (Denoted by ‘I’):  The rate of flow of net electric charge is called Current. Rate of flow means the amount of charge flowing through a particular area in unit time. If a net electric charge (Q) flows through a cross section of conductor in time t, then;

Where, I is electric current, Q is net charge and t is time in second.

SI unit of electric current is ampere (A).  One Ampere is the flow of electric charges through a surface at the rate of one coulomb per second i.e. one ampere is defined as one coulomb of charge following per second. Therefore;

Small quantity of Electric Current: Small quantity of electric current is expressed in milli-ampere and microampere. Milliampere is written as mA and microampere as μA

1mA (milliampere)= 10⁻³ A

1μA(microampere)=10⁻⁶ A

Ammeter: An apparatus to measure electric current in a circuit. It is always connected in series in a circuit. It has low resistance. It is represented by the symbol in an electric circuit.

 

Fig: Ammeter Symbol

Electric Circuit: Electric circuit is a continuous and closed path of electric current.

The electron can only flow when there is difference of electric pressure. It is analogues to “water flowing through a tube” It is only possible when there high pressure at one side and low at another side, then it will move from high pressure to low pressure.

In case of electric current, the flow of charge is made possible due to chemical action with in a cell that generates the potential difference across the terminals of the cell.

 

Example 1: Find the amount of electric charge flowing through the circuit if an electric current of 5 A is drawn by an electric appliance for 5 minute.

Solution: Given, electric current (I) = 5 A

Time (t) = 5 minute = 5 X 60 = 300 s

Electric charge (Q) =?

We know; I = Q/t

Or, Q = I x t

Or, Q = 5 A x 300 s = 1500 C

Example 2: If a current of 2 ampere is drawn for 1 hour through the filament of a bulb, find the amount of electric charge flowing through the circuit.

Solution: Given, electric current (I) = 2 A

Time (t) = 1 hour = 1 x 60 x 60 s = 3600 s

Electric charge (Q) =?

We know that Q = I x t

Therefore, Q = 2 A x 3600 s = 7200 C

 

Example 3: In how much time 6000 coulomb of electric charge will flow, if an electric current of 10 A is drawn through an electric motor?

Solution: Given, electric charge (Q) = 6000 C

Electric current (I) = 10 A

Time (t) = ?

We know; I = Q/t

Or, t = Q/I

Or, t = 6000 C ÷ 10 A = 600 s

Or, t = 10 min

Example 4: If an electric charge of 900 C flows through an electric bulb for half an hour, find the electric current drawn by the filament.

Solution: Given, electric charge (Q) = 900 C

Time (t) = Half an hour = 30 m = 30 x 60 = 1800 s

Electric current (I) =?

We know; I = Q/t

Or, I = 900 C ÷ 1800 s = 0.5 A

Example 5: If an electric charge of 15000 C flows through an electric iron for 5 minute, find the electric current drawn by filament of electric iron.

Solution: Given, electric charge (Q) = 1500 C

Time (t) = 5m = 5 x 60 = 300 s

Electric current (I) =?

We know; I = Q/t

Or, I = 1500 C ÷ 300 s = 5 A

Watch Video Lecture on Static Electricity👇: 

Static Electricity is the electric charge at rest on an object. Electric force is the force of attraction or repulsion on a charged particle due to an electric field. Electric field is the space around a charged object in which another charged object experiences electric force. Static Electricity (Hindi-Eng)

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Watch Video Lecture on How to determine Positive or negative charge 👇:

How can we determine positive or negative charge on an object?(Hindi-Eng)

Electroscope identify that the object is charged or not. electroscope not identify whether object is positive charged or negative charged.Watch Video Lecture 👇:

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