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physics

Practice 1

1.

Series Circuits
Parallel Circuits
OEk 1115 - Fundamentals of Electronics | Practice 1

2.

Outline
Series Circuits
Parallel Circuits
Applications of Ohm’s Law
Kirchhoff’s Voltage Law
Kirchhoff’s Current Law

3.

Series Circuits
A series circuit provides only one path for current between two points so that the
current is the same through each series resistor.

4.

Resistors in Series
Example. Calculate the total resistance RT, for each circuit.

5.

Resistors in Series
Example. Determine the value of R4 in the circuit.

Current in a Series Circuit
A milliammeter is connected between points A and B. It measures 50 mA. If you
move the meter and connect it between points C and D, how much current will it
indicate? Between E and F?

9.

Current in a Series Circuit
Example. Find the current in the circuit

10.

Current in a Series Circuit
Example. The current in the circuit is 1 mA. For this amount of current, what must
the source voltage Vs be?

11.

Current in a Series Circuit
Calculate the voltage drop across each resistor, and find the value of Vs.
To what value can be raised if the current is to be limited to 5 mA?

12.

Example of series-aiding voltage sources
Example. What is the total source voltage Vs(tot)?

13.

Kirchhoff’s Voltage Law
Example. Determine the unknown voltage drop, V3.

14.

Kirchhoff’s Voltage Law
Example. Find the value of R4.

15.

Voltage Divider
Example. Determine V1 (the voltage across R1) and V2 (the voltage across R2) in
the circuit.

16.

Voltage Divider
Example. Calculate the voltage drop across each resistor in the circuit.

17.

Power in Series Circuits
The power dissipated by each individual resistor in a series circuit contributes to
the total power in the circuit. The individual powers are additive.
The total amount of power in a series resistive circuit is equal to the sum of the
powers in each resistor in series.

18.

Power in Series Circuits
Power formulas are applicable to series circuits.
Since each resistor in series has the same current through it, the following
formulas are used to calculate the total power:

19.

Power in Series Circuits
Example. Determine the total amount of power in the series circuit.

20.

Power in Series Circuits
Solution 1:

21.

Power in Series Circuits
Solution 2:

22.

Voltage Measurements
Designate reference ground as the 0 V reference point for a circuit.
Voltage is always measured with respect to another point in the circuit.
The term ground has its origin in telephone systems in which one of the
conductors was the earth itself.
The term was also used in early radio receiving antennas (called aerials) where
one part of the system was connected to a metal pipe driven into the earth.
Today, ground can mean different things and is not necessarily at the same
potential as the earth.

23.

Voltage Measurements
In electrical wiring, the reference ground is usually the same as the earth potential
because neutral and earth ground are connected at the entrance point to a
building. In this case, reference ground and earth ground are at the same
potential.
The chassis serves as a return path for the electrical circuits in a vehicle.

24.

Measuring Voltages with Respect to Ground
When voltages are measured with respect to ground, they are indicated with a
single-letter subscript.
The ground point does not affect the current in the circuit or the voltage drops
across the resistors.

25.

Measuring Voltages with Respect to Ground
Example. Determine the voltages at each of the indicated points in each circuit
with respect to ground. Since each of the four resistors has the same value, 25 V
are dropped across each one.

26.

Parallel Circuits
When two or more components are individually connected between the same two
points, they are in parallel with each other.
A parallel circuit provides more than one path for current.
Each parallel path in a circuit is called a branch.
If there is more than one current path (branch) between two points, and if the
voltage between those two points also appears across each of the branches,
then there is a parallel circuit between those two points.