The document introduces basic concepts of electric circuits including charge, current, voltage, power, and circuit elements. It defines each concept, provides examples, and shows calculations for determining values like charge from given quantities of electrons or protons. Key points covered include that charge is measured in Coulombs, current in Amperes, voltage in volts, and power in watts. Circuit elements can be active sources or passive components that absorb energy.

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Chapter 1
Basic Concept
DKS1113 Electric Circuits

2. Electrical Safety
 “Danger—High Voltage.”
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3. Electrical Safety
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4. International Systems of Units
 The following are expressions of the
same distance in meters (m):
 600, 000, 000 mm
 600, 000 m
 600 km
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5. International Systems of Units
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6. Introduction to Electric Circuits
 An electric circuit is an interconnection of
electrical elements.
 Functions:
 To transfer energy from one point to another.
 Basic concepts:
 Charge.
 Current.
 Voltage.
 Power.
 Circuit elements.
 Energy.
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7. Charge – q(t)
 Basic quantity in an electric circuit.
 Defined as an electrical property of materials.
 Exist as negative (electron) and positive (proton)
charges.
 Measured in Coulombs (C).
 1 electron = -1.602*10-19C.
 Positive and negative charges move in
different direction.
 Creates electric current.
 Consider electric current as movement of positive
charge.
 Charge may be constant/varying.
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8. Charge – q(t)
Question:
 How much charge is represented by
4,600 electrons?
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9. Charge – q(t)
Solution:
Each electron has −1.602 × 10−19 C.
Hence 4,600 electrons will have
−1.602 × 10−19 C/electron × 4,600
electrons = −7.369 × 10−16 C.
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10. Current – i(t)
 Defined as the charge flow rate.
 Measured in Ampere (A).
 Current may be constant/varying.
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11. Current – i(t)
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12. Voltage – v(t)
 Defined to be the charge rate of doing
work.
 Energy required to move a unit charge
through an element.
 Measured in volts (V).
 Voltage may be constant/varying.
 1 volt = 1 joule/coulomb = 1 newton
meter/coulomb
 Voltage, ,
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13. Voltage – v(t)
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14. Power – p(t)
 Defined to be the time rate of doing work.
 Measured in watts (W).
 Power can be absorbed or supplied by circuit
elements.
 Positive power  element absorbs power.
 Negative power  element supplies power.
 ‘Sign’ determined by voltage and current.
 An ideal circuit:
 ∑Psupplied + ∑ Pabsorbed = 0.
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15. Energy
 Defined as the capacity to do work.
 Measured in joules (J).
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16. Example:
 An energy source forces a constant
current of 2 A for 10 s to flow through
a lightbulb. If 2.3 kJ is given off in the
form of light and heat energy, calculate
the voltage drop across the bulb.
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17. Solution
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18. Circuit Elements
 An element is the basic building block of a
circuit.
 Electric circuit is interconnecting of the
elements.
 Types of elements:
 Active elements Capable of generating energy
(i.e. batteries, generators).
 Passive elements  Absorbs energy (i.e. resistors,
capacitors and inductors).
 Voltage and current sources  the most important
active elements.
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19. Source
 Divided into:
 Independent source  Does not depend to
other elements to supply voltage or
current.
 Dependent source  Reverse of
independent.
 Constant voltage source:
 Voltage same for all elements.
 Constant current source:
 Current same throughout the circuits.
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20. Examples
 Calculate the amount of charge represented
by two million protons.
 Answer: +3.204 × 10−13 C.
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