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Chapter 16: Current Electricity

Download free PDF notes covering electric current definition (I = Q/t, rate of flow of charge), SI unit Ampere (A = Coulomb per second), conventional current (flow of positive charge from positive to negative terminal) vs actual current (flow of electrons from negative to positive terminal), Ohm's Law (V = IR, applies if temperature constant), resistance formula R = ρL/A (resistance proportional to length L and resistivity ρ, inversely proportional to cross-sectional area A), resistivity (ρ) as material property, Ohmic vs Non-Ohmic devices (Ohmic: linear I-V relationship like resistors; Non-Ohmic: non-linear behavior like diodes and transistors), EMF vs Potential Difference (EMF: total energy per unit charge in open circuit; Potential Difference: energy used between two points in closed circuit, always ≤ EMF due to internal resistance), ammeter connection (series, low resistance), voltmeter connection (parallel, high resistance), Ampere-hour (Ah) as unit of electric charge (Q = I × t), copper vs silver for household wiring (copper more cost-effective, comparable durability, more resistant to corrosion), current-carrying wire remains electrically neutral (equal electrons entering and leaving), and bending wire does not change resistance unless area or length changes - strictly according to FBISE 2026 SLOs.

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Chapter Overview & SLOs

What is electric current? Electric current (I) is the rate of flow of electric charge. Mathematically, I = Q/t, where Q is charge in Coulombs and t is time in seconds. The SI unit of current is the Ampere (A), defined as one Coulomb of charge passing a point per second.

What is the difference between conventional and actual current? Conventional current is defined as the flow of positive charge from the positive to the negative terminal, whereas actual current is the flow of electrons from the negative to the positive terminal.

What is Ohm's Law? Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points, provided the temperature remains constant. Mathematically, V = IR.

What is the formula for resistance? Resistance R = ρL/A, where ρ is resistivity (material property), L is length, and A is cross-sectional area. Resistance is directly proportional to length and resistivity, and inversely proportional to cross-sectional area.

What is the difference between Ohmic and Non-Ohmic devices?

| Type | I-V Relationship | Examples | |------|-----------------|----------| | Ohmic | Linear (straight line through origin) | Resistors, wires (at constant temperature) | | Non-Ohmic | Non-linear | Diodes, transistors, thermistors |

What is the difference between EMF and Potential Difference?

| Feature | EMF (Electromotive Force) | Potential Difference (PD) | |---------|---------------------------|--------------------------| | Definition | Total energy supplied per unit charge | Energy used between two points | | Circuit type | Open circuit | Closed circuit | | Value | Always greater than or equal to PD | Always ≤ EMF (due to internal resistance) |

How are ammeters and voltmeters connected in circuits?

  • Ammeter: Connected in series (low resistance) to measure current flow through the circuit.
  • Voltmeter: Connected in parallel (high resistance) to measure potential difference across a component.

Why is copper preferred for household wiring over silver? Although silver has slightly better conductivity, copper is used because it is much more cost-effective, has comparable durability, and is more resistant to corrosion at connection points.

What is an Ampere-hour (Ah)? Ampere-hour is a unit of electric charge. Q = I × t. For example, a 10 Ah battery can supply 10 A for 1 hour or 1 A for 10 hours.

These notes are strictly aligned with the Student Learning Outcomes (SLOs) for the FBISE 2026 annual examination.

  • How do we define electric current and its SI unit? Electric current ($I$) is the rate of flow of charge ($I = Q/t$); its unit is the Ampere (A), defined as one Coulomb of charge passing a point per second.
  • What are the limitations of Ohm's Law and the difference between Ohmic and Non-Ohmic devices? Ohm's Law ($V = IR$) only applies if temperature remains constant; Ohmic materials have a linear I-V relationship, while Non-Ohmic devices like diodes and transistors show non-linear behavior.
  • How do physical factors affect electrical resistance? Resistance is directly proportional to length ($L$) and resistivity ($\rho$), but inversely proportional to the cross-sectional area ($A$) ($R = \rho L/A$); bending a wire generally does not change its resistance unless it deforms the area or length.
  • How do we distinguish between EMF and Potential Difference (PD)? EMF is the total energy supplied by a source per unit charge (measured in an open circuit), while Potential Difference is the energy used between two points in a closed circuit and is always less than or equal to the EMF due to internal resistance.

Frequently Asked Questions (FAQ)

1. Are these Class 10 Physics notes based on the latest FBISE syllabus for 2026?
Yes, these notes are strictly designed according to the Student Learning Outcomes (SLO) provided by the Federal Board (FBISE) for the 2026 academic year. We regularly update our content to match the latest curriculum changes and exam patterns.

2. Do these Physics 16 notes include solved exercise questions and diagrams?
Absolutely. These notes contain comprehensive solutions to all textbook exercise questions, including Multiple Choice Questions (MCQs), Short Questions, and detailed Long Questions. We also include labeled diagrams and key definitions to help you secure maximum marks in your board exams.

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