Basics of Electricity

Basics of Electricity

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The potential difference in a circuit where the energy invested in carrying a charge of 4 coulombs is 4 joules is 1 volt. This can be calculated using the equation for the potential difference: V = W/Q, where V is the potential difference, W is the work done, and Q is the charge.

Basics of electricity: what is resistance?

Resistance is a measure of how much a component resists the flow of electric current. It is measured in Ohms (Ω). Ohm's law states that the potential difference (V) across a component is proportional to the current (I) flowing through it, with the constant of proportionality being the resistance (R). However, this only applies to ohmic materials.

To calculate the resistance of a circuit with a total potential difference of 2 volts and a total current of 0.17 amperes, we can use the equation R = V/I. Plugging in the values, we get:

R = 2V / 0.17A
R = 11.76 Ω

Therefore, the circuit has a resistance of 11.76 Ohms.

Basics of electricity: what is electric power?

Electric circuits involve the movement of charges and therefore have an associated power (energy per unit of time). The equation for electric power is:

P = V × I

where P is the power measured in watts (W), V is the potential difference in voltsV), and I is the current in amperes ( Ohm's law can be used to obtain the power in terms of two of the three basic quantities.

Electric circuits are made up of various components such as cables, resistors, switches, and power sources. These components are arranged in a specific way to create a circuit with a desired potential difference and current. The setup of the circuit determines its specific characteristics and possible applications.

Basic knowledge of circuits

Electric circuits can be described using diagrams that use standard symbols to represent each component in the circuit. The main components of a circuit include sources, wires, and resistors.

Sources are components that supply voltage and/or current to the circuit. Wires are used to transport the current from one component to another. Resistors are components that offer resistance to the flow of the current, limiting its flow.

Other complex devices can often be described in terms of their resistance and other conditions. For example, a lightbulb can be seen as a resistor that shines when a current flows through it.

An example of a basic circuit diagram is shown below. (Note: the cix symbol is not relevant for this discussion)

Diagram of a simple circuit
Diagram of a simple circuit

Resistance association

When there are multiple resistors in a circuit, it is important to understand the laws that govern their behavior. This knowledge can help us simplify circuits or achieve specific effects. The two main ways that resistors can be associated in a circuit are in series and in parallel.

Resistors in series are when n resistors are connected in a line on the same conductor or wire, without any branches. In this case, the resulting resistance of the set of resistors is simply the sum of their individual resistances:

R_total = R1 + R2 + ... + Rn

Resistors in parallel are when n resistors are connected on different branches that originate from a division of the same wire. In this case, the resulting resistance of the set of resistors is calculated using the following equation:

1/R_total = 1/R1 + 1/R2 + ... + 1/Rn

Understanding these laws can help in simplifying complex circuits or achieving specific effects with resistors.


Resistors connected in parallel
Resistors connected in parallel

Resistances in series: n resistors are on the same wire or conductor one after another. Resistances in parallel: n resistors are on different branches that originated from a division of the same wire.

Kirchhoff’s Laws

When analyzing circuits, there are two laws of conservation that are crucial to consider, known as Kirchhoff's laws:

  1. Conservation of current: At any node in a circuit, the total current entering the node must equal the total current leaving the node. This is based on the principle of conservation of charge, which states that charge cannot be created or destroyed, only transferred.
  2. Conservation of voltage: In a closed circuit or loop, the sum of the voltage supplied by all batteries or voltage sources must equal the voltage drop caused by every element in the loop. This is simply Ohm's law applied to closed circuits, which states that the voltage across a resistor is directly proportional to the current flowing through it.

By applying Kirchhoff's laws, we can accurately analyze and understand the behavior of complex circuits and ensure that they operate as intended.

Network of components
Network of components

Basics of Electricity - Key takeaways

Electric current is the number of charges that flow through a certain section of a conductor per unit of time. It is measured in amperes. The potential difference is the energy needed per unit of charge to move charges from one point to another. It is measured in volts. It is supplied by phenomena like chemical reactions, magnetic fields, non-renewable sources, etc. Resistance is the opposition of a substance to the flow of charge. It is measured in ohms. It is usually determined through Ohm’s law, a widely used approximation that relates it to the voltage and the current. In circuits, it is interesting to study how can we calculate the resistance of a set of resistors. The two usual positions are in series and parallel. In circuits, there are laws that capture the conservation of energy and charge that translate into the conservation of voltage and electric current. They are called Kirchhoff laws.

Basics of Electricity

Explain the principles of electric currents and basic electricity.

When a potential difference is established between two points, a flow of charges appears. The rate of this flow of charge is the electric current, which is determined by the potential difference and the resistance, i.e. the opposition of the medium to the movement of charges.

What is the basic unit of electric charge?

The basic unit of electric charge is the Coulomb (C).

What are the basic components of an electric circuit?

The basic components of an electric circuit are wires, batteries, and resistors.

What is voltage and power?

Voltage is the work needed per unit of charge to move charges between two points. Electric power is the rate of energy generated by a potential difference per unit time when charges are allowed to move.

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