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Introduction to Electricity: Exploring Electromagnetism and Electrical Circuit Analysis

This chapter provides an introduction to electricity, covering topics such as Thomson's plum pudding model, Rutherford model, and the concept of electrical charge. It also explores Coulomb's law, electric fields, electric potential, and voltage. The chapter emphasizes the ability to analyze electromagnetic forces and construct and measure circuits.

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Introduction to Electricity: Exploring Electromagnetism and Electrical Circuit Analysis

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  1. | Faculty Engineering Technology Chapter 1 Physics Technology Introduction to Electricity Najihah Abdul Rashid

  2. Course outcome 1 Electromagnetism - Ability to explain and analyze the concept of magnetic field and electromagnetic force

  3. Course outcome 2 Electrical – ability to explain Ohm’s Law and Kirchhoff’s law and determine loads in series or parallel. Ability to construct the circuit and measures the electrical parameters using measuring tools.

  4. What is electricity?

  5. Thomson’s Plum pudding model Rutherford model Inside an atom Charge cloud model

  6. The atom An atom is a fundamental unit of matter made up of protons (with a positive charge) neutrons (neutral – no charge) electrons (with a negative charge)

  7. What is electricity? Everything is made of atoms which contain POSITIVE particles called PROTONS and NEGATIVE particles called ELECTRONS. Proton (+) Electron (-) Neutron Figure 1.1: an atom

  8. Cont. An atom will usually have the same number of positives and negatives This makes the atom NEUTRAL. Proton (+) Electron (-) Neutron

  9. Electrical Charge Electric charge is given the symbol Q Electrons are the charge carriers that flow in an electrical circuit – from the negative to positive terminals.

  10. Electrical Charge Charge is measured in Coulombs which is given the symbol C

  11. Coulomb’s law There are two kinds of charges – positive and negative charges. Like charges repel and unlike charges attract. Coulomb’s law is about the forces between point charges Where the constant of proportionality, K = 9.0 x 10 9 N m2 C-2

  12. Example 1.1 Three point charges of +2 µC, -3 µC and +4 µC are fixed at their respective positions as shown in figure 1.2. Calculate the force on the charge of -3 µC by the other two charges +2 µC 5 m 3 m +4 µC -3 µC Figure 1.2: example 1.1 4 m

  13. Electrical Charge The charge on a proton is 1.6 x 10-19C which is the same size as the charge on an electron.

  14. What is electricity? • Electrons have a negative charge (Q) measured in coulombs (C). • Electrons move round a circuit from negative to positive (remember like charges repel, opposites attract) giving rise to an electric current

  15. Cont Figure 1.3: Static electricity

  16. What is electricity? So electricity is… movement of charge round a circuit. We call this electric current.

  17. Electric field • Electric field is defined as the electric force per unit charge • The direction of the field is taken to be the direction of the force it would exert on a positive test charge. • The electric field is radially outward from a positve charge and radially in toward a negative point charge

  18. Cont Figure 1.4: Electric field

  19. Electric potential The electric potential V, is defined as the electric potential energy, U, per unit charge Or

  20. Electric potential The amount of electrical energy the electrons have at any point in a circuit is known as their “potential”. As they move the electrons transfer energy into other forms. This means at any two points the electron has different amounts of energy.

  21. Cont Figure 1.5: Electron movement

  22. What is the energy change which takes place in a battery?

  23. When a battery is in a circuit The electrical energy is carried by the electrons that move round the circuit It is converted into others forms of energy.

  24. Electrons start with (for example) 6J of energy. They have “potential”. • As they pass through the bulb, some of the energy is converted to light. • Electrons which have passed through the bulb have less energy. Or less “potential”. There is a “potential” difference in the circuit

  25. What is electricity?What is a voltage? What is a volt?

  26. What has “potential difference” got to do with voltage? It is the same thing! The potential difference (p.d.), or voltage, of a battery is a measure of the electrical energy given to one coulomb of charge passing through the battery

  27. Potential Difference or Voltage (V) A 9 V battery will give how much energy to each coulomb of charge passing through the battery?

  28. Potential Difference or Voltage (V) A 1.5 V battery will give how much energy to each coulomb of charge passing through the battery?

  29. Voltage or p.d. Voltage (or p.d.) is measured in volts and is given the symbol V

  30. How can we measure voltage? Voltage (or p.d.) can be measured using a voltmeter. An ammeter is connected in the circuit but a voltmeter must be connected across the component. V

  31. Example 1.2 Two point charges of 2.00 µC and 8.00 µC are separated by a distance of 5.00 mm. A point P is at distance of 4.00 mm from the 2.00 µC charge and 3.00 mm from the 8.00 µC charge • Find the electrical potential at point P • What is the electric potential energy of a charge of 5.00 µC at P?

  32. END

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