UNIT 8.

ELECTRICAL AND
ELECTRONIC CIRCUITS
PHYSICS AND CHEMISTRY
2º ESO
EVA VICTORIA MARCOS ROBLES
1. Electrical circuits
2. Electrical quantities
3. Series circuist
4. Parallel circuits
1. ELECTRICAL CIRCUITS
All of these devices work with electricity. When we press a switch, many electrons start to flow.
These electrons provide the energy to make an electrical appliance work, to light a bulb or to
play music on your mobile
Electric current is a continuous flow of electric charges. When these charges flow through a
conductor, we call them electrons

An Electric circuit is a set of connected components which an electric current flows through
BASIC COMPONENTS AND CIRCUIT DIAGRAMS
These diagrams both show the same circuit:

This table shows the function, symbols and appearance of the basic components of an electrical circuit
2. ELECTRICAL QUANTITIES
Is the measure of the energy available to move electrons around a circuit
Voltage (V)
The amount of energy depends on its electrical tension or voltage (V). It´s
measured in SI units called volts

Electric Is the charge, measured in coulombs, that flows through a point in the
current circuit in one second. It´s measured in SI units called amperes (A)

Electrical Is the measure of how easily electrons flow through the components of a
resistance circuit. It´s measured in SI units called ohms (Ω)
MESAURING ELECTRICAL QUANTITIES

Mesauring voltage Mesauring electric current Mesauring resistance

Voltmeter. We connect Ammeter. We connect this Ohmmeter. We connect

the cables from the is so that all the current the cables to the
voltmeter in parallel to flows through it opposite ends of the
the component resistor that´s
disconnected from the
circuit
ELECTRICAL RESISTANCE AND OHM´S LAW
The electrical current in a circuit is directly proportional to the voltage
but inversely proportional to the resistance

𝑉
𝐼=
𝑅
EXERCISES TO DO IN CLASS

Example 2: In a circuit with a resistor and a 20 V battery, a current of 0.2 A

circulates. Calculate the value of said resistance.

Example 3: What will be the voltage supplied by a battery knowing that

when connected to a circuit in which there is a 45 Ω resistance, the intensity
is 0.1 A. (Sol.: 4.5 V)
3. SERIES AND PARALLEL CIRCUITS
Series circuit Parallel circuit

The electric current that flows The potential difference of

through the components is the each component is the same.
same. The battery voltage is The intensity supplied by the
distributed between them generator is distributed
between them
SERIE CIRCUITS
The elements are connected like the links of a chain (the end of one with the
beginning of the other).
The output of one to the input of the next and so on until the circuit is closed

The total resistance of the circuit is equivalent to the sum of the two individual resistances:
𝑅𝑇 = 𝑅1 + 𝑅2 + 𝑅3 + ⋯
The voltage drop across the total circuit is determined by the voltage source, typically a battery. This is
often labeled on your circuit diagram, next to two or more parallel lines of different length. The voltage
drops across each component of the series circuit add up to the total voltage drop across the circuit.
𝑉𝑇 = 𝑉1 + 𝑉2 + 𝑉3 + ⋯
A series circuit only has one path for this flow, so the current is the same at all points on the circuit.
(There are no branches to split the current.) As long as you know the voltage and resistance at any
point on the circuit (or for the circuit as a whole), you can use Ohm's Law to find the current:
𝐼 = 𝑉 / 𝑅.
𝐼𝑇 = 𝐼1 = 𝐼2 = 𝐼3 = ⋯
EXAMPLE
𝑅𝑇 = 2 + 6 + 4 = 12Ω
𝑉𝑇 = 5𝑉
𝑉 5
𝐼 = = = 0.42 A
𝑅 12
𝐼𝑇 = 𝐼1 = 𝐼2 = 𝐼3 = 0.42 𝐴
𝑉1 = 0,42 ∙ 2 = 0,84𝑉
𝑉2 = 0,42 ∙ 6 = 2,52𝑉
𝑉3 = 0,42 ∙ 4 = 1,64𝑉
EXERCISES
PARALLEL CIRCUITS
The elements have their inputs connected to the same point of the circuit and their
outputs to the same point of the circuit

1 1 1
The total resistance of the circuit is: 𝑅𝑇 = + + +⋯
𝑅1 𝑅2 𝑅3
The voltage: 𝑉𝑇 = 𝑉1 = 𝑉2 = 𝑉3 + ⋯
Current: 𝐼𝑇 = 𝐼1 + 𝐼2 + 𝐼3 + ⋯
EXAMPLE

1 1 1
The total resistance of the circuit is: 𝑅𝑇 = + + = 0,367Ω
10 5 15
The voltage: 𝑉𝑇 = 5
5
Current: 𝐼1 = = 0,5𝐴
10
5
𝐼2 = = 1 𝐴
5
𝐼3 = 5/15 = 0,33
𝐼𝑇 = 𝐼1 + 𝐼2 + 𝐼3 = 0,5 + 1 + 0,33 = 1,83𝐴
EXERCISES
Presentation unit 8 (1 point)
You have to do a canva infographic (only 1 page) about electricity
generation, transport and storage.
In addition, you have to take and interpret a label from any
electronic device you have at home, attach the photo, just like the
one that appears on page 203 of your book, and interpret it as in
the book. Do another page in the infographic