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resistance

Primary Information
Secondary Information

Definition

Resistance is the property of a material that opposes the flow of electric current. It is measured in ohms.

Resistance is caused by the interactions of electrons with the atoms of the material. When an electric current flows through a material, the electrons collide with the atoms of the material. These collisions slow down the electrons and make it more difficult for them to flow through the material.

The resistance of a material depends on the material's composition, its temperature, and its size. Materials with a high concentration of free electrons, such as metals, have low resistance. Materials with a low concentration of free electrons, such as insulators, have high resistance.

Resistance is important in electrical circuits. It is used to control the flow of electricity and to protect circuits from damage. For example, a resistor is a device that is used to add resistance to a circuit. Resistors are used in a variety of applications, such as voltage dividers, current limiters, and power supplies.

How can the word be used?

The doctor found that the patient had developed a resistance to the antibiotic.

resistance

Different forms of the word

Noun:

  • the opposition to or the power of opposing something.
  • the ability to withstand something, such as heat or pressure.
  • a military force that opposes an enemy.

Etymology

The word "resistance" comes from the Latin word "resistere", which means "to stand against".

The first recorded use of the word "resistance" in English was in the 14th century.

Question

What is resistance?

AQA Science Exam Question and Answer

Question:

Explain the concept of electrical resistance and how it affects the flow of current in an electrical circuit. Provide an example of a material with high resistance and its implications in practical applications.

Answer:

Electrical resistance is the opposition offered by a material to the flow of electric current. It is caused by collisions between electrons and atoms within the material. Resistance is measured in ohms (Ω) and determines how much current can flow through a given material at a certain voltage.

In an electrical circuit, resistance limits the flow of current. According to Ohm's law (V = I × R), where V is voltage, I is current, and R is resistance, an increase in resistance for a constant voltage leads to a decrease in current. This relationship is crucial for designing and optimising circuits, ensuring the safe and efficient operation of devices.

An example of a material with high resistance is rubber or plastic, often used as insulation around wires. While these materials are poor conductors, they are excellent insulators due to their high resistance. This property prevents unwanted current leakage and protects users from electric shock. High resistance is also used in resistors to regulate current flow in electronic components.

Understanding resistance is essential in designing circuits, managing power consumption, and ensuring the safe and efficient operation of electrical devices. Balancing resistance with other circuit parameters allows engineers to create systems that fulfil specific requirements and functions.