Electric current/CBSE/Grade-10/Physics

Added: 2026-05-11

[00:02:31]Hello students, welcome to the student brand.

[00:02:39]Hello students, welcome to the student brand. This is Today we are going to discuss about electric current. So what is electric current?

[00:02:50]Electric current is not a electric current. So the rate of flow of charge the flow of charge through a unit cross-sectional area per second is called electric current I = Q byt right so we are taking I = Q byt the rate of flow of charge through a cross-sectional area per second that is called electric current of current is amp SI unit of current is ampere and SI unit of charge is kum.

[00:03:55]So we can take C here we can take capital A and time is second.

[00:04:03]Yes. So 1 ampere is defined as 1 kum of charge flowing through unit cross-sectional area per second. 1 ampere is defined as 1 kum of charge flowing through unit cross-sectional area per second that is 1 ampere. So if they ask in the exam define 1 ampere of current. So 1 kum of charge flowing through cross-sectional area per second uh through a unit cross-sectional area per second.

[00:04:44]Okay. So that is about 1 ampere.

[00:04:49]Now here you can see inside of the conductor there are number of charges are moving right number of charges are moving in the conductor. Will you say only one electron flows current is flowing? Will you say only two electrons flows current is flowing? Will you say only three electrons flows current is flowing. We can't say like that. Right?

[00:05:12]Number of charges are moving in the conductor then only we can say current is flowing.

[00:05:19]Then only we can say current is flowing.

[00:05:23]So here you can see positive charge, negative charge, positive charge, negative charge. So charges are moving like this.

[00:05:33]Positive charges are moving at the same time. Negative charges are there in the conductor.

[00:05:39]So that's why Q is Q you are taking plus or minus N. N is the number of electrons and one electron 1.6 6 into 10^ -19 kum and one electron and 1 electron 1.6 into 10^ -9 kum in 1 kum. So if you are taking 1 by 1.6 into 10^ -19 then you'll get 1 by 1.6 into 109.

[00:06:17]If you do this 0.62 625 into 1019.

[00:06:24]If you solve 6.25 into 10^ 18 electrons are present in one column in one column 6.25 into 25 into 10^ 18 electrons are present. So I hope it is very clear understood or not. So observe carefully here. So electric current the rate of flow of charge at the flow of charge through a unit cross-sectional area per second is called electric current. SI rate unit rate of current is ampere. Sin rate unit of charge is column. SI unit of time is second. 1 amp equal to 1 colum per 1 second.

[00:07:05]Okay. So number of charges are moving in the conductor. So that's why charge is quantized.

[00:07:12]So Q = plus or minus N and one electron 1.6 into 10 - 19 column in 1 column 1 by 1.6 into 10 - 19. So if it is goes you'll get 0.625 into 10^ 19. So I hope you'll get 6.25 into 10^ 18 electrons in 1 column 6.25 into 10^ 18 electrons are present. So I hope it is very clear understood or not.

[00:07:40]The next now so we'll discuss about electrical elements. Okay, electrical appliances. Electrical elements or electrical appliances. We'll discuss about it. So here you can see first one cell positive terminal negative terminal cell and coming to the battery.

[00:08:33]This is a battery positive terminal negative terminal. So two or more cells together battery. And coming to the third one open switch closure switch.

[00:08:48]So this is the open switch.

[00:08:51]Open switch.

[00:08:55]Okay. And the next one fourth one is closed switch.

[00:09:01]Only the dot is there. If dot is there that is closed switch. If dot is not there that is open switch. So this the closed switch closed switch.

[00:09:17]And coming to the fifth one.

[00:09:21]So resistor resistor resistor is a device.

[00:09:32]Resistor is a device which is used to oppose the electric current.

[00:09:36]Resistor is a device which is used to oppose electric current. Rio start. So here I'm talking about Rio start.

[00:09:46]This is Rio start.

[00:09:50]Rio start.

[00:09:53]So real start is a device which is used to regulate the current. Read is a device which is used to regulate the current without changing the voltage source.

[00:10:07]Without changing the voltage source I hope it is very clear. Understood or not? Cell battery open switch closed switch resistor Rio start. Understood or not? I hope it is very clear. once again. So now you can observe here cell battery open switch close switch resistor start and coming to the seventh one amter.

[00:10:36]Ameter is a device.

[00:10:39]So positive term, negative terminal.

[00:10:42]Ameter is a device which is used to measure the current. Ameter is a device which is used to measure the electric current. So am will be connected in series combination.

[00:10:54]So coming to voltmeter positive terminal negative terminal.

[00:11:02]Ameter is a device which is used to measure the electric current. Ameter will be connected in series combination.

[00:11:11]Voltter is a device which is used to measure the potential difference. This voltmeter will be connected parallel combination to the circuit. And coming to the ninth one wire joining. So this a wire joining and 10th one wire crossing.

[00:11:31]Wire crossing and 11th one.

[00:11:34]11th one here you can observe bulb electrical bulb.

[00:11:43]So once observe all these electrical appliances okay cell battery open switch closer switch resistor RIO start ameter voltmeter wire joining wire crossing electrical bulb.

[00:12:05]So I hope it is very clear. So these are related to electrical elements.

[00:12:15]Electrical elements. I hope it is very clear.

[00:12:18]Understood or not?

[00:12:21]Yes. Next. So we'll discuss about electric circuit.

[00:12:28]Electric circuit.

[00:12:56]A closed and continuous path of an electric current is known as an electric circuit.

[00:13:02]A closed and continuous path of electric circuit.

[00:13:18]Electric circuit. a closed and continuous path of an electric current.

[00:13:24]Okay. So here bulb this the bulb and your emitter battery key switch positive terminal negative terminal current is flowing right. So bulb is glowing like this.

[00:13:53]Understood or not? So I hope it is very clear. So a continuous and closed path of an electric circuit is known as electric current. A continuous and closed path of an electric current.

[00:14:07]Electric current is known as an electric circuit. An electric circuit. So here we are to discuss about two points. Those are conventional current and electric current. Sir, what do you mean by conventional current and what do you mean by electric current? Conventional current is nothing but so before finding before knowing electron, proton, neutron scientists were given that statement the flow of positive charges will be taken the direction of flow of electric current. The direction of flow of electric current.

[00:14:53]Okay. So here positive charges are moving from positive terminal to negative terminal. Positive charges are moving from positive terminal to negative terminal. Whereas electrons are moving from negative terminal to positive terminal. Electrons are moving from negative terminal to positive terminal. Whereas positive charges are moving from positive terminal to negative terminal. I hope it is very clear. And one more point here.

[00:15:23]So positive terminal has high potential whereas negative terminal has low potential. So conventional current conventional current and the second one is electric current.

[00:15:44]Electric current conventional current.

[00:15:47]So positive charges are moving from high potential to low potential.

[00:15:53]Positive charges are moving from high potential to low potential. Whereas electrons are moving from low potential to high potential. So they will ask one question in the board exam. Will electrons flows from high potential to low potential or low potential to high potential? Electrons always will move from low potential to high potential in the circuit.

[00:16:18]Okay. So here you can observe and electrons. So positive charges are moving from high potential to low potential whereas electrons are moving from low potential to high potential.

[00:16:31]Low potential to high potential. So this about conventional current and this is about electric current. So I hope it is very clear. This is about electric circuit.

[00:16:42]This is about electric circuit. Is it clear? So I hope it is very clear. Next one. So we'll discuss about potential difference and electrical potential.

[00:16:58]Potential difference and electrical potential.

[00:17:14]Potential difference.

[00:17:20]Potential difference.

[00:17:31]Potential difference.

[00:17:33]What are potential difference?

[00:17:36]Potential difference is nothing but work done to bring unit positive charge.

[00:17:44]So here you can take this the conductor point A and point B. We are doing some work.

[00:17:55]We are doing some work to bring unit positive charge from point A to point B.

[00:18:03]We are doing some work to bring unit positive charge from point A to point B.

[00:18:10]Okay. So V = W by Q. So positive charge V = W by Q work done to bring unit positive charge from one point to another point within the conductor V = W by Q 1 vol= to 1 J of work is done to bring one cool charge 1 volt is defined as one J of work is done to bring one cool charge one volt is defined as one J of Work is done to bring one kum of charge from one point to another point within the conductor. That is very very important within the conductor.

[00:18:52]within the conductor. Right? So coming to electrical potential.

[00:18:59]Electrical potential.

[00:19:04]Electrical potential.

[00:19:14]Electrical potential.

[00:19:16]Here you can see this the positive charge infinity.

[00:19:22]This is the required field to this a point.

[00:19:26]We are doing some work to bring unit positive charge from infinity to the required field from infinity to the required field. So we are doing some work. So V = W by Q 1 volt = 1 J of work is done to bring one colum of charge from infinity to the required field is called electrical potential.

[00:19:52]So we yes positive charge infinity.

[00:19:57]Okay. So V = to W by Q.

[00:20:02]Okay. So here you need to understand sir what is the difference between potential difference and electrical potential.

[00:20:09]So coming to potential difference.

[00:20:12]So work done to bring unit positive charge from one point to another point within the conductor is called potential difference. Electrical potential is nothing but work done to bring unit positive charge from infinity to the required field. from infinity to the required field that is electrical potential. So very very important that is a difference. So you have to keep in mind so instead of writing potential difference if you write electrical potential then you do mistakes.

[00:20:45]Okay. So potential difference must be there within the conductor. Electrical potential means from infinity to the required fit. Okay. So I hope it is very clear understood or not. So this is about potential difference and electrical potential.

[00:21:03]So next we will discuss about Ohm's law.

[00:21:13]Oh is very very important.

[00:21:17]Ohm is nothing but the potential difference across the ends of the given metallic conductor is directly proportional to current flowing through it at a constant temperature.

[00:21:34]So once again the potential difference across the ends of the given metallic conductor is directly proportional to current flowing through it at constant temperature.

[00:21:46]So that is about Ohm's law definition understood or not? So here you can see V is directly proportional to Ohm's law.

[00:22:00]V is directly proportional to V= R.

[00:22:06]V is directly proportional to V= R.

[00:22:09]Ohm's law gives the definition of resistance.

[00:22:13]Ohm's law gives the definition of resistance.

[00:22:18]Okay. So materials required. What are the materials required?

[00:22:24]Materials required.

[00:22:29]Okay. First one is micro wire.

[00:22:34]Four cells. We have to take four cells.

[00:22:40]Four cells.

[00:22:43]Four cells.

[00:22:45]1.5 volt of each cell is 1.5 volt potential difference. And the next one is nicro wire.

[00:22:58]Necroire.

[00:23:01]Okay. Necroirus length is 0.5 m length.

[00:23:07]0.5 m length.

[00:23:12]Okay. Coming to third one ameter.

[00:23:18]Fourth one voltmeter.

[00:23:24]And the sixth one is fifth one is key key and the sixth one is connecting wires.

[00:23:46]Okay. So these are materials required.

[00:23:49]Once again observe four cells 1.5 volts of each nicro 0.5 m length amter voltmeter key connecting wires key is nothing but switch key is nothing but switch here we can take switch and connecting wires. So next one circuit diagram circuit diagram.

[00:24:16]So circuit diagram must be there.

[00:24:20]Okay, I'll draw the circuit diagram.

[00:24:22]Then we'll go to the process.

[00:24:41]Circuit diagram.

[00:24:53]So here four nikrome cells. 1 2 3 4 Ameter resistor Switch multimeter. Uh so Here we are drawing the dotted lines because one by one we are connecting.

[00:25:55]Okay, one by one we have to connect.

[00:25:57]That's why I'm drawing the dotted line.

[00:25:59]Right? So first so this is circuit diagram. Next one procedure procedure is first one connect one cell and note down the reading of ometer and voltmeter.

[00:26:19]We have to connect one cell first. After that you have to note down the reading of a meter and multimeter.

[00:26:28]Next connect two cells and again same process.

[00:26:34]So repeat the process.

[00:26:37]So note down the reading of a and voltmeter.

[00:26:40]So repeat the same process for three and four cells.

[00:26:46]Three and four cells.

[00:26:49]and table column.

[00:26:52]So I'll draw the table column. Okay. So I have to mention in the table column.

[00:26:58]So here you can see this the table column serial number of cells amid reading voltage reading V by okay. So here you can observe.

[00:27:12]So serial number number of cells am omit reading voltage reading V by I = R 1 2 3 4 1 2 3 4 because we are using four cells right so we have to connect one by one so that's why and if you draw the graph for Ohm's law the graph is VA on yaxis I on X-axis the graph is straight line.

[00:27:44]For omic conductor for omic conductor the graph is straight line. For nonomic conductor the graph is curve.

[00:27:52]So here you have to observe V on Yaxis I on X-axis.

[00:27:56]The graph is curve for nonomic conductors. Sir what do you mean by omic conductors?

[00:28:03]Nanomic conductor. The conductors which obey Omar those are called omic conductor. The conductor which does not obey ohms those are called nonomic conductors.

[00:28:14]Okay. So I hope it is very clear. Next So omic conductors and nonomic conductors completed.

[00:28:53]So that is about ohms law. Next one resistors are connected in sorry factors depends on resistance.

[00:29:02]So resistance is directly proportional to length of the conductor.

[00:29:08]Resistance is inversely proportional to area of the cross-section.

[00:29:12]R is directly proportional to L by A. R= row into L by A. Sir, what is meant by So what is the meaning of row? R = row into L by A. So R is a resistance.

[00:29:32]R is a resistance. Row is the resistivity.

[00:29:37]Row is the resistivity.

[00:29:42]Okay. R is a resistance.

[00:29:44]Row is a resist meeting.

[00:29:47]Understood or not?

[00:29:49]So I hope it is very clear.

[00:29:52]Just check once.

[00:29:56]Okay. Now, so resistance, resistance and resistivity. We'll discuss resistance and resistivity.

[00:30:10]resistance and resistivity.

[00:30:16]So resistance depends on length and area of the cross-section and here it does not depend on length and area of the cross-section.

[00:30:28]So second one is S unit of resistance is ohm. Third one is symbol here length and area of the cross does not depend length and area of the cross-section. So here you can take from your row = A by L.

[00:30:48]Row = A by L. Now row = m² by m get cancel.

[00:30:59]Okay. So resistivity is ometer and so we can say ometer.

[00:31:11]Okay.

[00:31:26]And your resistance depends on temperature.

[00:31:31]And your resistivity also depends on temperature.

[00:31:36]And your resistance depends on nature of the material.

[00:31:44]Nature of the material.

[00:31:50]And your resistance also depends on resistivity also depends on nature of the material.

[00:32:02]Okay. So I hope it is very clear. These are the points. Just check once.

[00:32:11]Okay. R is directly proportional to R is inversely proportional to area.

[00:32:17]Till now we discussed about it. Next one. Resistors are connected in series and resistors are connected in parallel.

[00:32:56]resistors are connected in series combination. Next one, resistors are connected in parall combination. Here they will ask one question. Which physical quantity is constant in series combination? Which physical quantity is constant in parall combination?

[00:33:14]Okay, that question is very very important. So we'll discuss that point here. You can see resistors are connected in series combination.

[00:34:21]So from Ohm's law I so I = I1 + I2 + I3 sorry I is constant right I is same throughout the circuit I = I1 = I2 = I3 = I current is same But potential difference is different in series combination. Right? Potential difference is different. Then we can write V = V_sub_1 + V_sub_2 + V3.

[00:35:07]IS = I1 I R2 + I R3.

[00:35:16]I am taking common R1 + R2 + R3. I get cancel RS = R1 + R2 + R3.

[00:35:32]So this the formula RS = R1 + R2 + R3.

[00:35:37]If a number of resisters are connected in par combination RS = to NR.

[00:35:46]Okay. So I hope it is very clear.

[00:35:50]Next one coming to par combination.

[00:36:25]So resistors are connected in par combination.

[00:36:29]So here you can observe.

[00:36:33]So resistors are connected in par potential difference is same current is different.

[00:36:44]current is different right?

[00:36:47]So positive term and inter current is flowing R1, R2, R3.

[00:36:59]Here potential difference is same.

[00:37:08]Current is dividing I1, I2, I3.

[00:37:14]So here the same current is flowing here but across R1 R2 R3 current is dividing across R1 R2 R3 current is dividing right. So here you can observe R1 R2 R3 I1 I2 I3 current is dividing. So from ohms V= I from Ohm's law V = I = V by R. Then IP = I1 + I2 + I3.

[00:37:50]V by RP = V by R1 + V by R2 + V by R3.

[00:37:58]So V I am taking common 1x rp = 1x r1 + 1x r2 + 1x r3. So VB get cancel.

[00:38:12]VB get cancel. The remaining values are 1x rp = 1x r1 + 1x r2 + 1x r3.

[00:38:24]Okay. If n number of resistors are connected 1x rp= n by rp = r by n.

[00:38:36]So I hope it is very clear. This a this about resistors are connected in par combination. The final formula is very important. 1x rp= 1x r1 + 1x r2 + 1x r3.

[00:38:49]Okay. Yes. Next.

[00:39:22]Now heating effect of electric current.

[00:39:26]Heating effect of electric current.

[00:39:36]Okay. So, V = W by Q.

[00:39:42]V = W by Q. W = VQ.

[00:39:47]So, P = rate of doing work.

[00:39:51]VQ by T.

[00:39:54]VQ by T. So we know the flow of charge the rate of flow of charge is called current.

[00:40:02]So Q byt is called current I.

[00:40:06]Then P = V into Q byt is I. P = VI.

[00:40:13]So energy is equal to P into T.

[00:40:17]Then we can take H = V I into T. Then H = I R into I into T. Then H = I² RT.

[00:40:36]Heat produced in the conductor is directly proportional to square of current. Heat produced in the conductor is directly proportional to resistance.

[00:40:47]Heat produced in the conductor is directly proportional to time. So this is about electric current.

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