AP Unit III C 2

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AP Unit III C 2

• Steady state direct current circuits with
  batteries and resistors only

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• a) Students should understand the behavior of
  series and parallel combinations of resistors, so
  they can
• (1) Identify on a circuit diagram whether
  resistors are in series or parallel.
• (2) Determine the ratio of the voltages across
  resistors connected in series or the ratio the
  currents through resistors connected in parallel.
• (3) Calculate the equivalent resistance of a
  network of resistors that can be broken down into
  series and parallel combinations.

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• (4) Calculate the voltage, current, and power
  dissipation for any resistor in such a network of
  resistors connected to a single power supply.
• (5) Design a simple series-parallel circuit that
  produces a given current through and potential
  difference across one specified component and
  draw a diagram for the circuit using conventional
  symbols

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• (b) Students should understand the properties of
  ideal and real batteries, so they can
• (1) Calculate the terminal voltage of a battery
  of specified emf and internal resistance from
  which a known current is flowing.
• (2) Calculate the rate at which a battery
  supplying energy to a circuit or is being charged
  up by a circuit.

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• (c) Students should be able to apply Ohms Law
  and Kirchoffs rules to direct current circuits
  in order to
• (1) Determine a single unknown current, voltage,
  or resistance.
• (d) Students should understand the properties of
  voltmeters and ammeters, so they can
• (1) State whether the resistance of each is high
  or low.
• (2) Identify or show correct methods of
  connecting meters into circuits in order to
  measure voltage or current

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Series Circuits

• The resistance in a series circuit is equal to
  the sum of the resistances around the circuit.
• RT R1 R2 R3

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Parallel Circuits

• The total resistance an a parallel circuit is
  from the inverses of the individual resistances
• 1/ RT 1/R1 1/R2 1/R3

R1
R2
R3
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• If a series circuit has 3 resistors each of 15 O,
  calculate the total resistance in the circuit.
• If a parallel circuit has 3 resistors each of 15
  O, calculate the total resistance in the circuit.
• Three resistors in parallel, 15 O, 25 O, 35 O.
  Calculate the total resistance in the circuit.

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Kirchoffs Laws

• First Law At a junction the total current
  entering the junction is equal to the total
  current leaving the junction
• Second law The net e.m.f. (electromotive force)
  around a circuit loop is equal to the sum of the
  p.d.s around the loop.

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Voltmeters

• Voltmeters are connected in parallel ACROSS the
  component they are measuring the potential
  difference of.
• They have a high internal resistance so
  negligible current goes through them.

V
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Ammeters

• Have low resistance and measure the current going
  THROUGH the circuit so must be connected in
  SERIES with the components.

A