Activities

Current, Voltage, Resistance and Power

The objective of this activity is to practise the comprehension of a written text and write the answers in well-structured and complete sentences.

Current is the flow or movement of electrical charges. Current is electrons in motion. Electrons flow from a wire connected to a source of electrical energy. Voltage is the pressure that pushes the electrons and causes them to flow. It is the force caused by electrons repelling each other. Resistance is the interference to flow of electrons. Since electrons are charged particles, we can also say that resistance is the opposition to the flow of charges. Resistance is the law that limits or controls the current. Power is the amount of work done when voltage pushes current through resistance. Current, Voltage, Resistance and Power are all interrelated. They are different aspects or characteristics of the same phenomenon we call electricity.

Some letter symbols have been developed in order to refer to these important concepts in electricity and electronics, to make it easier to speak about them. For current, the letter symbol is “I”. It stands for the “Intensity” of the current. The letter “C” was not ideal because it could be confused with the letter “C” for Coulomb. The other three letters are easier to remember because they are simply the first letter of the word.

All of them have their units of measure. Current is measured in Ampers (A), or Amp, and it is the number of Coulombs of electrical charge moving past a point per second. Fuses are rated in the amount of current or Amps that they can handle before burning out. The Ampere was named for the French physicist André-Marie Ampere, who created theories and performed experiments related to current flow.

Voltage is measured in Volts (V). A Volt is the amount of force necessary to move electrical current. Matter is rated by the number of Volts of pressure. For example, a house outlet can have 120 V of electrical pressure. The Volt was named in honour of count Alessandro Voltaire, who developed the first electrochemical cell and battery.

Resistance is measured in Ohms (Ώ). Ohms measure the amount of interference to current flow. Ohm was named after George Simon Ohm, who identified the relation between current, voltage and resistance.

Power is measured in Watts (W). A Watt is how much work is done as current flows through a load or resistance. It takes about 750 Watts to equal one Horse power. Light bulbs in many appliances are rated in Watts. Watt is named after James Watt, who developed the practical steam engine capable for doing a great deal of work.

- What makes electrons move in an electric circuit?
- What is resistance?
- What does “I” stand for?
- Which is the unit used to measure current? **Mantinc "what"**
- What are Ohms? Why do they have this name?
- What was James Watt's invention?

A la solució, una mica més del mateix:

1. Voltage pushes them and makes them move.
2. Resistance is the interference to the flow of electrons.
3. “I” stands for current.
4. The unit to measure current is the Ampere, or Amp.
5. Ohm is the unit to measure resistance. Ohms are named after George Simon Ohm, who identified the relation between current, voltage and resistance.
6. James Watt’s invention was the steam machine.

Comprehension questions:

1. What makes electrons move in an electric circuit?
2. What is resistance?
3. What does “I” stand for?
4. What is the unit used to measure current?
5. What are Ohms? Why do they have this name?
6. What was James Watt’s invention?

1. Voltage pushes them and makes them move.
2. The resistance is the interference to the flow of electrons.
3. “I” stands for current.
4. The unit to measure current is the Ampere, or Amp.
5. Ohm is the unit to measure resistance. Ohms are named after George Simon Ohm, who identified the relation between current, voltage and resistance.
6. James Watt’s invention was the steam machine.

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Electric current
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