Electric circuits basic concepts

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Electric circuits basic concepts
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The atom
Nucleus Protons () and neutrons Electrons (-)
rotating on orbits or energy bands which are
called shells Valence electrons Electrons that
are in the orbits farther from the nucleus
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Categories of Materials

• Conductors
• They have large number of free electrons. (Silver
  and copper)
• Semiconductors
• Do not carry current as easily as conductors the
  have four valence electrons. This material is
  used to make semiconductor devices.
• Insulators
• Poor conductors, very few free electrons

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Electric charge

• The proton and the electron exhibit a force of
  attraction due to their electrical charge. The
  proton is said to be charged positive() and the
  electron negative(-). They have the same
  magnitude but opposite charge.
• The electron electric charge is 1.6 x 10-19
  Coulombs.

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Unit of charge

• Q unit of charge
• Q is given in Coulombs.
• 1 coulomb 6.25 x10 18 electrons.
• Current is the flow of electric charge.
• A 1 amp of current 1
  coulomb /second.

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Components required in an electric circuit

• Supply or source
• Electric component
• Connection between supply and component.
• Close path from supply to ground.

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Basic electric circuit
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Voltage sources
Battery
Solar cell
Power supply
Generator
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Basic quantities in an electric circuit

• Voltage given in volts (V)
• Current given in amps (A)
• Resistance given in ohms (?)

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Voltage

• This is the driving force in electric circuits
  and it is what creates the current.
• Voltage is also called potential difference
• A voltage is measure with a voltmeter or a
  multimeter set to measure voltage.

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Electric Current

• Electric current is the result of the electrons
  moving inside the conductor due to the potential
  difference applied.
• For current to exist, there has to be a potential
  difference applied and a closed path across the
  potential.
• The more voltage is applied, more current will
  result.
• Current is measured with a multimeter set to
  measure current. To measure current, all the
  current to be measured has to go into the meter
  and out of the meter.

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Resistance

• It is the characteristic of an element to oppose
  current flow. The more resistance, the less
  current flow and vise versa.
• All electronic elements have some resistance in
  them.
• Resistors are used to control current flow.
• Resistance is measure with a multimeter set to
  measure resistance.

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Measuring a voltage
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Measuring current
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Measuring resistance
The value of resistance is given in ? (ohms). No
voltage should be present when measuring
resistance.
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Basic voltage current and resistance
relationshipOHMS law

• Voltage resistance current
• Current voltage/resistance
• Resistance voltage/current
• Power VI
• Symbol for current I (amps)
• Symbol for voltage V (volts)
• Symbol for resistance ? (ohms)
• Symbol for power w (watts)

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Basic Electrical components
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Resistors
Used mainly to control current flow. Resistance
is the property of the resistors because they
oppose current flow. Its unit is Ohm (?) and its
symbol R, R 50 ohms, 5Kohms.
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Capacitors
Use to store energy The property of the capacitor
to store energy is called capacitance and it is
given in a unit call Farads (F), its symbol is C,
C 1UF, 100UF
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Inductors
Inductors store energy and this property is
called inductance. The symbol for inductance is L
and its value is given in Henrys.(H) L 100mH,
10mH.