Study S2 Science Science - Electrical System - Geniebook

Electrical Systems

In this article, the following are the objectives that will be discussed.

  • Describe some examples of electrical systems.
  • Draw the various parts of a circuit.
  • Explain how electricity travels.

 

What are some examples of electrical systems?

Examples of electrical systems are digital watches, light bulbs and kitchen appliances such as the oven, microwave and electric kettle.

Credits: Johannes Plenio

How do these systems work?

Let's take the example of an electric kettle. 

When the button on the electric kettle is pressed, the circuit closes. This allows electricity to flow through the circuit.

 

What are the fundamental components of an electrical circuit?

The fundamental components of an electric circuit are the wire and the energy source (battery).

 

Electrical circuit

How are the components represented in an electrical circuit diagram

 

 

Question 1:

Which of the following components are required for electricity to flow in an electrical circuit?

 

  1. battery, bulb, switch
  2. battery, switch, wire
  3. switch, wire, bulb
  4. switch, bulb, fuse

 

Solution: 

(B) battery, switch, wire

Explanation:

The wire and battery is needed to form a loop to allow electricity to flow in an electrical circuit.

Answer:

(B) battery, switch, wire

 

 

Question 2:

Which of the following does not show an example of an electrical system?

 

  1. a kettle that uses a stove to boil water
  2. a mobile phone
  3. an oven
  4. a speaker system that emits loud sounds

 

Solution:

(A) a kettle that uses a stove to boil water

 

 

Question 3: 

Draw a series and parallel circuit which contain two dry cells, a switch and two light bulbs.

 

Solution:

                   

  bulbs are arranged in series              bulbs are arranged in parallel

 

 

Question 4:

How can the components be arranged in a circuit?

 

Solution: 

The bulbs can be arranged either in series or in parallel.

When the bulbs are arranged in series, both bulbs will have the same current flowing through them. When more cells are added to the circuit, the brightness of the bulbs will increase as more energy is available.

When the bulbs are arranged in parallel, both bulbs will have the same voltage. The bulb with the lower resistance will conduct more current and therefore shine brighter.

 

 

Question 5:

Which of the following does this symbol represent?

 

 

 

  1. dry cell
  2. variable resistor
  3. fixed resistor
  4. ammeter

 

Solution:

(C) fixed resistor

 

 

Question 6:

How does the brightness of a bulb increase in a circuit with 2 dry cells?

 

  1. Place more bulbs in series within the circuit.
  2. Remove 1 dry cell from the circuit.
  3. Add additional dry cells to the circuit.
  4. Remove all the dry cells in the circuit.

 

Solution: 

(C) Add additional dry cells to the circuit.

 

Explanation:

By adding more dry cells to a circuit, the amount of energy increases, thus increasing the current flowing through the light bulb. Hence, the light bulb will shine brighter.

Answer: 

(C) Add additional dry cells to the circuit.

 

 

What is electricity?

  • Electricity is defined as the flow of electric charges (electrons). 
  • Only in a closed electric circuit can electric charges flow. 
  • The rate of flow of electrical charge is known as current (I). 
  • The SI unit of electric current is ampere (A).

 

How do we measure current? 

 

 

An ammeter measures the amount of electric charges moving through a circuit. It is connected in series.

 

 

Question 7:

What is the definition of electric current?

 

  1. Electric current is the rate of change of electric charge.
  2. Electric current is the rate of flow of electric charge.
  3. Electric current is the total number of electrons.
  4. Electric current is the total number of protons.

 

Solution:

(B) Electric current is the rate of flow of electric charge.

 

 

Question 8:

What instrument is used to measure current, and how should it be connected?

  1. voltmeter, connected in series
  2. voltmeter, connected in parallel
  3. ammeter, connected in series
  4. ammeter, connected in parallel

 

Solution:

(C) ammeter, connected in series

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