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# Electrical Energy Questions and Answers

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Introduction

Electrical Energy in the Home:

1. One of the main advantages of electricity is that it can be moved with comparative ease from one place to another through Electric Current.
• Describe the behaviours of electrostatic charges and the properties of the fields associated with them
• Electric charges are associated with sub-atomic particles
• Electric fields surround electric charges such that another electric field placed within that field will experience a force
• Two types of charges: Positive (Protons) and Negative (Electrons)
• Two like charges will repel but opposite charges will attract
• + and – charges are usually able to affect neutral objects
• Define the unit of electric charge as the coulomb
• The unit of measuring charge is the coulomb (C)
• The coulomb itself is a large unit such that one coulomb of charge is equivalent to the magnitude of the charge carried by 6.24 X 10 18 electrons
• Therefore the magnitude of a charge carried by an electron is    16.24 ×1018  C
• The charge for one electron is -1.602 X 10-19 C
• The charge for one proton is +1.602 X 10-19 C
• Describe the behaviour of electrostatic charges and the properties of the fields associated with them
• Define the electric field as a field of force with a field strength equal to the force per unit charge at that point E=Fq
• An electric field is a region in which a charged particle will experience a force
• An electric field is a vector quantity, which means it must have both magnitude and direction
• Strength of an electric field at any point is defined as the size of the electric force action on a unit of charge
• Direction of an electric field at any point is defined as the direction of the force on a positive charge when placed at this point
• Present diagrammatic information to describe the electric field strength and direction
• Although an electric field is a region of influence, it is represented though lines, when using line to represent electric fields, the following applies:

Middle

• Describe electric potential different (voltage) between two points as the change in potential energy per unit charge moving from one point to the other (joules/coulomb or volts)
• In order to move the charges, energy is required. This energy is known as voltage or potential difference in the context of electricity
• Differing from gravitational potential energy, as seen in the analogy, electric potential energy difference or voltage takes into account the size of the charge. Unlike energy, which is measured in joules, potential difference or voltage in electricity is measured in JC-1 or volt (V)
• 1 V = C-1
• There are two important facts in relation to the definition of voltage:
• A power source, such as a battery, is the most common supply of voltage, the negative terminal of the power source is said to have zero energy. Therefore, the voltage is equal to the electric potential energy of the positive terminal
• Only positive charges move down the electric potential gradient
• Voltage or potential difference is defined as the change in energy when one unit of

Conclusion

Mathematically:
• Describe qualitatively how each of the following affects the movements of electricity through a conductor: length, cross-sectional area, temperature, material
• Resistance varies between different materials, four factors affect this
• The length of the conducting material:
• Resistance is directly proportional to the length of the conducting material, the longer the material, the higher the resistance.
• This is because the longer the material, the higher chance of electrons colliding with the lattice (arrangement of atoms for most conducting materials), This impeded their movement making it difficult to pass through.
• Cross-sectional area of the conducting material:
• Resistance is inversely proportional to the cross sectional area of the conducting material
• A smaller cross section area will make it difficult fro electrons to move through the material and they have more chance of colliding with the lattice
• Temperature:
• Temperature of the material is directly proportional to Resistance of the material
• This is because as the temperature rises, the lattice will vibrate therefore increases the probability of collisions between electrons and the lattice
• Types of Material:
• Some conducting materials have more free electrons per unit volume then others that are available to carry electricity and pass through the lattice
• Therefore the amount of free electrons per unit volume is inversely proportional to resistance of the material.

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