Current Electricity

​ Electricity and Magnetism

• The Phenomenon of producing magnetism by electric current is called Magnetic Effect of Current

• The Phenomenon of producing electricity by magnetism is called Electromagnetic Induction

​Hence Electricity and Magnetism are interrelated

​Electric Current

​Click here to view the introductory video

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Click here to view the video on difference between Current and potential (Potential difference)​ PD spotted video Click here

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Another Video​
Other PD Spotted Video Click here

​ Charge

1. ​A metal contains numerous free electrons which is responsible for the flow of electric current hence called conductor.

2. ​On the other hand, insulators does not contain free electron ​and hence does not conduct electricity.

3. ​For ​the flow of electric current, free electrons for solid conductor and ions for liquid conductor is responsible

​Note:

​Potential differences can be created/established by:

1. Connecting with batteries (Produce DC )

2. ​Connecting with main line (Produce AC)

Basic ​Electrical Components​

​The electric circuits are closed-loop or paths, forming a network of electrical components where electrons can flow. To draw the circuit diagram symbols aside are used to represent different electrical components:

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Click here for a video​

​Electric Circuits​

​A Simple Electric Circuits​

​Terminal Voltage

​Electrical Resistance

The obstructions/hindrance to the flow of electric current is called Electrical Resistance.

​Electrical Resistance

​Click here for a video on the concept of Electrical Resistance

​what is resistors and its uses in the electronic device

Electrical Resistors​

• An electrical resistor is an electrical component that limits or regulates the flow of electrical current in an electronic circuit.

• They are made up of various materials like carbon or graphite, nickel-chromium alloy, nickel, tin oxide, etc

• Resistors are used for many purposes.

  1. limiting electric current

  2. voltage division

  3. heat generation

  4. matching and loading circuits

  5. gain control

  6. setting time constants

Types of Electrical Resistors​

​Click here for video

​Click here for a simulation of Ohm's law

Note:​

• Ohm’s law is not a universal law. Some conductors like liquid electrolytes, diode, thermistor, LDR, etc., do not obey Ohm’s law as the resistance vary with voltage and current.

• Therefore based on Ohm's law, conductors can be classified as Ohmic conductors and Non-Ohmic Conductors. So conductors which obey Ohms law is called Ohmic Conductor and which does not obey is called Non-Ohmic Conductor. ​

1. If 0.6A current flows through a resistor. Voltage of two points of resistor is 12V. What is the resistance of the resistor?

2. If the resistance of an electric iron is 50 Ω and a current of 3.2 A flows through the resistance. Find the voltage between two points.

3. A potential difference across 24 Ω resistor is 12 V. What is the current through the resistor?

​Numerical Questions on Ohm's Law

The voltage-current graphs for some of the ohmic and non-ohmic conductors are discussed below:

​I-V Graph for Resistors with Temp constant

For each devices students are asked to make short notes including the points:
1. I-V graph for the device
2. What is the use of device?
3. Is it ohmic or non-ohmic conductor?
4. Relation between the I and V (State what happens when v varies)

cont...

cont...

​Verification of Ohm's Law

​Click here for the virtual Lab

Multiple Choice

The given graph shows the relationship between the potential difference across a resistor and the current flowing through it. At which intervals does the resistor obey Ohm’s law?

• PQ and RS

• OR and ST

• PQ and QR

• QR and ST

Click here to watch a video on electrical resistivity

• ​The resistivity of a conductor is also called as specific resistance.

• The resistivity of a material does not depend upon the shape and size of the conductor​.

• It depends only upon the resistance and nature of material of the conductor​.

• The reciprocal of resistivity is called electrical conductivity (σ =1/resistivity).​

• Resistivity for most materials increases with increase in temperature​ except for semiconductors (eg: selicon) the resistivity decreases with increase in temp.

​Investigating variation of current with change in resistanceActivity

​Click here for virtual lab - to set up the apparatus as shown below:

​Activity: Investigating variation of current with change in resistance

​Record the reading as shown below

Review Questions on Ohm's law

​The voltage-current curve for an ohmic conductor is plotted as shown in the figure below. What is the resistance of resistors 1 and 2?

Review Questions on Ohm's law

​A student conducts an experiment and measures the current and voltage across two unknown resistors. Then she/he plots her/his finding in a current-voltage coordinate, as shown in the figure. What can be concliuded about resistors A and B?

​Potential Drop/Voltage Drop

1. ​Conductors carrying current always have inbuilt resistance to oppose the current flow.

2. Potential Drop/ Voltage drop is defined as the amount of voltage loss that occurs through all or part of a circuit due to resistance.

3. The greater the resistance of the circuit, the higher the voltage drop that occurs. 

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The electrical energy loss due to voltage drop is generally transformed to some other forms of energy like heat energy (Heating appliance), light energy (Bulb), mechanical energy (Washing machine), etc., in the various appliances​

​ Heating effect of current

• ​The phenomenon in which heat is produced by the passage of electric current in a conductor is called thermal effect of current or heating effect of current.

  Click here for a video Explanation​-how heat is produced, Click here for its application

​ Heating effect of current

• ​The amount of heat produced in a conductor is given by H =I²R t, Where I is the current, R - resistance and t-time of passage of current.

• Therefore, the heat produced depends upon the strength of current flowing through it, the resistance of the conductor and the time for which the current is passed through it​

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Electric Power

• ​Click Here for a video explanation

• Power in general is defined as the rate of doing work (energy)

Electric Power

Electric Power

​Click here for chapter Revision Questions