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Chapter 17: Problem 9

What is an insulator?

Short Answer

Expert verified
An insulator is a material that resists the flow of electric current, such as rubber or glass.

Step by step solution

01

Understanding Materials

Materials can be classified into three main categories based on their ability to conduct electricity: conductors, insulators, and semiconductors. Conductors allow electricity to flow through them easily, while insulators do not.
02

Defining an Insulator

An insulator is a type of material that resists the flow of electric current. This means it does not allow electricity to pass through it effectively.
03

Examples of Insulators

Common examples of insulators include rubber, glass, and plastic. These materials are often used to coat or support electrical connections to prevent accidental shocks or short circuits.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Conductors
Conductors are materials that permit the easy flow of electric charge. They possess free electrons, which are loosely bound to atoms, allowing them to move freely through the material. This movement of electrons creates an electric current. Most metals are excellent conductors due to their atomic structure. They have a 'sea of electrons' that can detach and move when an electrical field is applied.

Some key points about conductors:
  • Copper and aluminum are common conductors due to their high conductivity and low resistance.
  • Conductors are used in making electrical wires and components to facilitate quick and efficient transmission of electricity.
  • Temperature can affect a conductor's ability to carry electricity: as temperature increases, their resistance may also increase, reducing their effectiveness slightly.
Understanding conductors is crucial in developing efficient systems for transporting electricity and designing electrical circuits.
Semiconductors
Semiconductors sit between conductors and insulators in terms of their ability to conduct electric current. They conduct electricity under certain conditions, which makes them highly valuable in electronics. Semiconductors have a conductivity level that is neither too high, like metals, nor too low, like insulators. Instead, their conductivity can be manipulated through doping鈥攁 process of adding impurities to alter electrical properties.

Key characteristics of semiconductors include:
  • Silicon and germanium are two widely used semiconductor materials.
  • They are fundamental in producing components like diodes, transistors, and integrated circuits.
  • Semiconductors can be made more conductive by applying voltage or light, making them ideal for computer chips and solar cells.
Semiconductors form the backbone of modern electronics, facilitating advancements in technology by allowing control over electrical conductivity.
Electric Current Resistance
Resistance is the property of a material that opposes the flow of electric current. It is a crucial concept in understanding electrical systems. Conductors have low resistance, allowing current to flow easily. On the other hand, insulators have high resistance, preventing current flow. The resistance of a material is influenced by several factors, including its temperature, length, cross-sectional area, and the material type.

Some important considerations about electric current resistance:
  • The resistance of a wire increases with its length and decreases with its cross-sectional area.
  • Ohm's Law, represented as \( V = IR \), describes the relationship between voltage (V), current (I), and resistance (R).
  • Materials with high resistance are used to create components like resistors, which control the flow of current in a circuit.
By controlling resistance, engineers can design circuits that distribute power efficiently and safely to various components in an electronic system.

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Most popular questions from this chapter

The yeast gene \(S E R 3\), which has a role in serine biosynthesis, is repressed during growth in nutricnt-rich medium, so little transcription takes place and little SER3 enzyme is produced. In an investigation of the repression of the SER3 gene, a region of DNA upstream of SER3 was found to be heavily transcribed when SER3 is represed (). A. Martens, L. Laprade, and F. Winston. 2004. Nature \(429: 571-574\) ). Within this upstream region is a promoter that stimulates the transcription of an RNA molecule called SRGI RNA (for SER3 regulatory gene 1 ). This RNA molecule has none of the sequences necessary for translation. Mutations in the promoter for SRGI result in the disappearance of SRG I RNA, and these mutations remove the repression of \(S E R 3\). When RNA polymerase binds to the \(S R G\) I promoter, the polymerase is found to travel downst ream, transcribing the SGRI RNA, and to pass through and transcribe the promoter for \(S E R 3\). This activity leads to the repression of SER3, Propose a possible explanation for how the transcription of SGRI might repress the transcription of \(S E R 3\), (Hint: Remember that the \(S G R I\) RNA does not encode a protein.)

Briefly list some of the ways in which siRNAs and miRNAs regulate genes.

Malaria, one of the most pervasive and destructive of all infectious diseases, is caused by protozoan parasites of the genus \(P\) lasmodium, which are transmitted from person to person by mosquitoes. Plasmodium parasites are able to evade the host immune system by constantly altering the expression of their var genes, which encode Plasmodium surface antigens (L. H. Freitas-Junior et al. \(2005 .\) Cell \(121: 25-36\) ). Individual var genes are expressed when chromatin structure is disrupted by chemical changes in histone proteins. What type of chemical changes in the histone proteins might be responsible for these changes in gene expression?

How does bacterial gene regulation differ from eukaryotic gene regulation? How are they similar?

What will be the effect of a mutation that destroys the ability of poly(A)-binding protein (PABP) to attach to a poly(A) tail?
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