# Current Electricity

## Overview

Current electricity is a fundamental concept in physics that deals with the flow of electric charge in a circuit. In this course, we will delve into various aspects of current electricity, focusing on key topics such as electromagnetic force (emf), potential difference (p.d.), current, internal resistance of a cell, and lost Volt.

One of the primary objectives of this course is to differentiate between electromagnetic force, potential difference, current, and internal resistance of a cell. Understanding these concepts is crucial as they form the basis of electrical circuits and their behavior. By grasping the differences between these terms, students will be able to analyze circuit parameters effectively.

Another key objective is to apply Ohm’s law to solve problems related to current electricity. Ohm’s law states that the current flowing through a conductor is directly proportional to the potential difference across it, provided the temperature remains constant. By mastering Ohm’s law, students will be equipped to calculate unknown electrical quantities in circuits.

The course also covers the measurement of resistance using techniques such as the meter bridge. The meter bridge is a useful tool that allows for precise determination of resistance in a circuit. By learning how to use the meter bridge, students can accurately measure resistance and understand its significance in circuit analysis.

Furthermore, students will explore the concepts of resistance in series and in parallel, as well as their combinations. Understanding how resistances behave in series and parallel configurations is essential for designing and analyzing complex circuits. By studying these configurations, students will gain insights into optimizing circuit performance.

Moreover, the course will introduce students to the potentiometer method of measuring emf, current, and internal resistance of a cell. The potentiometer is a versatile instrument that offers high precision in measuring electrical quantities. By utilizing the potentiometer, students can accurately measure key parameters in a circuit.

Lastly, the course will delve into electrical networks and the application of Kirchoff’s law. Kirchoff’s laws, including Kirchoff's voltage law and Kirchoff's current law, are fundamental principles in circuit analysis. By applying these laws, students can solve complex network problems and understand the behavior of current in circuits.

## Objectives

1. Determine The Resistivity And The Conductivity Of A Conductor
2. Differentiate Between Emf, Pd, Current And Internal Resistance Of A Cell
3. Measure Emf, Current And Internal Resistance Of A Cell Using The Potentiometer
4. Use Metre Bridge To Calculate Resistance
5. Apply Kirchoff’s Law In Electrical Networks
6. Identify The Advantages Of The Potentiometer
7. Apply Ohm’s Law To Solve Problems

## Lesson Note

Current electricity is the flow of electric charge across an electrical field or circuit. It is the basis of many of the technological advancements we enjoy today, such as lighting, heating, and powering various electronic devices.

## Lesson Evaluation

Congratulations on completing the lesson on Current Electricity. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

1. What is the formula for calculating potential difference (p.d.) in a circuit? A. V = IR B. V = I/R C. V = I x R D. V = R/I Answer: B. V = I/R
2. What is the SI unit of current? A. Volts B. Watts C. Amperes D. Ohms Answer: C. Amperes
3. Which of the following best describes Ohm's Law? A. Resistance is directly proportional to voltage B. Current is inversely proportional to resistance C. Current is directly proportional to voltage D. Voltage remains constant in a circuit Answer: C. Current is directly proportional to voltage
4. What is the function of the internal resistance of a cell in a circuit? A. To generate electrical energy B. To control the flow of current C. To increase the potential difference D. To provide stability to the circuit Answer: B. To control the flow of current
5. In which configuration does the total resistance in a circuit decrease - series or parallel? A. Series B. Parallel Answer: B. Parallel
6. Which instrument is commonly used to measure resistance accurately? A. Ammeter B. Voltmeter C. Ohmmeter D. Galvanometer Answer: C. Ohmmeter
7. What is the principle behind the operation of a potentiometer in measuring emf? A. Kirchoff's law B. Joule's law C. Principle of moments D. Wheatstone bridge principle Answer: D. Wheatstone bridge principle
8. How is the conductivity of a conductor related to its resistivity? A. They are inversely proportional B. They are directly proportional C. They are not related D. Conductivity depends on temperature only Answer: B. They are directly proportional
9. Which law is used to analyze complex electrical networks? A. Faraday's law B. Newton's law C. Kirchoff's law D. Ohm's law Answer: C. Kirchoff's law

## Past Questions

Wondering what past questions for this topic looks like? Here are a number of questions about Current Electricity from previous years

Question 1

Which of the following pairs of musical instruments produce sound due to the vibration of air column?

Question 1

Which of the following is a type of wave that is both mechanical and longitudinal?

Question 1

You are provided with a battery of e.m.f, Estandard resistor, R, of resistance 2 Ω $\mathrm{\Omega }$, a key, K, an ammeter, A, a jockey, J, a potentiometer, UV, and some connecting wires.

(i) Measure and record the emfE, of the battery.

(ii) Set up the circuit as shown in the diagram above with the key open.

(iii) Place the jockey at the point, U, of the potentiometer wire. Close the key and record the reading, i, of the ammeter.

(iv) Place the jockey at a point on the potentiometer wire UV such that d = UT = 30.0 cm.

(v) Close the circuit, read and record the current, I, on the ammeter,

(vi) Evaluate I1 ${}^{1}$.

(vi) Repeat the experiment for four other values of d = 40.0 cm, 50.0 cm, 60.0 cm and 70.0 cm. In each case, record I and evaluate I1 ${}^{1}$.

(vii) Tabulate the results

(ix) Plot a graph with d on the vertical axis and I on the horizontal axis stalling both axes from the origin (0,0).

(x) Determine the slope, s, of the graph.

(xi) From the graph determine the value I1 ${}_{1}$, of when = 0. (ci) Given that=s, calculate 8.

(xii) State two precautions taken to ensure accurate results.

(xii) Given that Eδ $\frac{�}{�}$ = s, calculate δ $�$.

(b)(i) Write down the equation that connects the resistance, R, of a wire and the factors on which it depends. State the meaning of each of the symbols.

(ii) An electric fan draws a current of0.75 A in a 240 V circuit. Calculate the cost of using, the fan for 10 hours if the utility rate is \$ 0.50 per kWh.

Practice a number of Current Electricity past questions