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Maharashtra State BoardSSC (Marathi Semi-English) 9th Standard [इयत्ता ९ वी]
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Syllabus

Potential and Potential Difference

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Topics

  • Electrostatic Potential
  • Potential Difference
  • Experiment 1
  • Experiment 2
  • Experiment 3

Electrostatic Potential:

Water or liquids naturally flow from a higher level to a lower level, and heat transfers from a warmer object to a cooler one. In a similar way, positive electric charges move from a point with a higher electric level to a point with a lower electric level. This electric level, which governs the direction of charge flow, is referred to as electrostatic potential.

Electrostatic potential can be thought of as an "electric height" or level that drives the movement of electric charges, much like the height difference drives the flow of water. It is this difference in electrostatic potential between two points that causes charges to move, creating an electric current. This concept is fundamental to understanding how electricity flows in circuits.

Potential Difference:

Electric charges flow in a circuit because of a potential difference, which is the difference in electrostatic potential between two points in the circuit. This potential difference acts as a driving force that causes electric charges to move, such as:

  • Water flows in a waterfall due to a difference in height.
  • Heat transfers from one object to another due to a difference in temperature.

Similarly, in an electric circuit, charges move from a point of higher potential to a point of lower potential. The potential difference ensures that the electric current flows, just as a height difference ensures the flow of water. Without a potential difference, there would be no movement of charges and thus no current in the circuit.

Potential difference of a cell:

  • The difference in potential between the positive and negative terminals of a cell is the potential difference of that cell. This potential difference is caused by chemical reactions occurring inside the cell.
  • The potential difference sets the electrons in motion and results in the flow of electricity through a conducting wire connected to the two ends of the cell.
  • The amount of work done to carry a unit positive charge from point A to point B is called the electric potential difference between the two points.

Potential difference between two points = `"Work"/" Total charge transferred"`, V = `"W"/"Q"`

1 V = `"1J"/"1C"` The unit of potential difference in SI system is volt.

Experiment 1

1. Aim: To observe the flow of electric current in a circuit and understand the role of potential difference.

2. Requirements: copper connecting wires, a light bulb, and a 1.5 V dry cell (battery).

3. Procedure

  • Build a circuit with copper wires and a light bulb as shown in Fig. a. The bulb does not light up because there is no current.
  • Connect a 1.5 V dry cell as in Fig. b. The bulb lights up, indicating current flow.
  • Electrons move from the negative to the positive terminal due to the potential difference created by the dry cell.
  • Conventional current flows in the opposite direction of electron movement.

(a) Electrical Circuit

 (b) Electrical Circuit

4. Conclusion: The bulb does not light up in the circuit without a cell because there is no potential difference to drive the current. When a cell is connected, a potential difference is applied, causing current to flow and the bulb to light up. The SI unit of potential difference is Volt (V), and the SI unit of electric current is Ampere (A), which is defined as 1 Coulomb of charge passing through a wire per second.

Experiment 2

1. Aim: To observe the flow of water due to the difference in levels and relate it to the concept of electric potential.

2. Requirements: Two plastic bottles, a rubber tube, a clamp, and water.

3. Procedure

  • Set up the two bottles as shown in the figure.
  • Connect the bottles with a rubber tube.
  • Fill one bottle with water while keeping the other empty.
  • Use a clamp to stop water flow in the tube.
  • Remove the clamp and observe what happens.

Level of water and direction of flow

4. Observations: When the clamp is removed, water flows from the bottle with a higher level to the one with a lower level. The flow stops when the water levels in both bottles become equal.

5. Conclusion: Water flows due to the difference in levels between the two bottles. Similarly, in electricity, the flow of electric charges depends on the electric potential difference between two points. Just as water stops flowing when levels are equal, electric charges stop moving when the potential difference becomes zero. To keep water (or electricity) flowing, a constant difference in level (or potential) must be maintained. This experiment demonstrates how a difference in levels (for water) or potential (for electricity) drives flow.

Experiment 3

1. Aim: To demonstrate how a potential difference causes the flow of charges between two points.

2. Requirements: two conductors (A and B), a conducting wire, and insulated stands for safety.

3. Procedure

  • Place conductor A at a higher potential (positive charge) and conductor B at a lower potential (negative charge).
  • Connect the two conductors using a conducting wire.
  • Observe the flow of electrons from B (lower potential) to A (higher potential).

Potential difference and flow of electricity

4. Observation: Electrons flow from conductor B to conductor A because of the potential difference. The flow of electrons continues until the potential difference between A and B becomes zero.

5. Conclusion: A potential difference between two points drives the flow of charges. Positive charges move from higher to lower potential, while electrons (negative charges) move from lower to higher potential. Work is required to move a positive charge against the electric field, from lower to higher potential. This experiment explains how potential difference causes electric current in a circuit.

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Related QuestionsVIEW ALL [153]

Name the law which relates the current in a conductor to the potential difference across its ends.

Two charged spherical conductors of radius R1 and R2 are connected by a wire. Then the ratio of surface charge densities of the spheres (σ1/σ2 ) is ______

Define the following:
Potential difference

Point out two differences between e.m.f. and potential difference as applied to electric circuits.

The values of current I flowing in a given resistor for the corresponding values of potential difference V across the resistor are given below:

I (amperes) 0.5 1.0 2.0 3.0 4.0
V (volts) 1.6 3.4 6.7 10.2 13.2

Plot a graph between V and I and calculate the resistance of that resistor.

Three electric cells of potential difference 1.5 V each have been connected as a battery. The potential differences of the battery will be ____________ V.

Calculate the quantity of heat produced in a 20 Ω resistor carrying 2.5 A current in 5 minutes.

Write down the formula which states the relation between potential difference, current, and resistance.

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