# What factors affect resistivity?

There are several factors that affect the resistance of a conductor;

• material e.g. copper has lower resistance than steel.
• length – longer wires have greater resistance.
• thickness – smaller diameter wires have greater resistance.
• temperature – heating a wire increases its resistance.
• What is the difference between resistance and resistivity?

The resistance of an object (i.e., a resistor ) depends on its shape and the material of which it is composed. Resistivity ρ is an intrinsic property of a material and directly proportional to the total resistance R, an extrinsic quantity that depends on the length and cross-sectional area of a resistor.

## What is the name of the symbol for resistivity?

Symbols and Units Resistivity is usually represented by the Greek letter rho (ρ), and is measured in Ω m. Conductivity is usually represented by the Greek letter sigma (σ), and is measured in S m−1.

## How can resistance be useful?

However, it is resistance that allows us to use electricity for heat and light. Therefore, it is sometimes useful to add components called resistors into an electrical circuit to restrict the flow of electricity and protect the components in the circuit.

## What is the unit of the resistance?

The ohm (symbol: Ω) is the SI derived unit of electrical resistance, named after German physicist Georg Simon Ohm.

## What affects resistivity of a wire?

There are several factors that affect the resistance of a conductor; material e.g. copper has lower resistance than steel. thickness – smaller diameter wires have greater resistance. temperature – heating a wire increases its resistance.

## What is resistivity Class 10?

The resistivity of a material is the resistance of a wire of that material of unit length and unit cross-sectional area. The unit for resistivity is the ohm-metre. The resistivity of a material depends on its nature and the temperature of the conductor, but not on its shape and size.

## How length can affect resistance?

Resistance increases with length because the electrons have further to go, so suffer greater collisions with atoms in the material. Look at these wires: Electrons moving through the short wire only feel resistance for a short time compared to the longer one. This means its resistance is less.

## How do you measure conductivity?

It is the reciprocal of electrical resistivity (ohms). Therefore conductivity is used to measure the concentration of dissolved solids which have been ionized in a polar solution such as water. The unit of measurement commonly used is one millionth of a Siemen per centimeter (micro-Siemens per centimeter or µS/cm).

## What is the cause of resistance?

Resistance – Higher tier. An electric current flows when electrons move through a conductor, such as a metal wire. The moving electrons can collide with the ions in the metal. This makes it more difficult for the current to flow, and causes resistance.

## Why is it important for an ammeter to have a low resistance?

An ammeter is an instrument for measuring the electric current in amperes in a branch of an electric circuit. It must be placed in series with the measured branch, and must have very low resistance to avoid significant alteration of the current it is to measure. By contrast, an voltmeter must be connected in parallel.

## Why does temperature affect resistance?

The more the atoms jostle around in the material, the more collisions are caused and hence the greater the resistance to current flow. In a material where the resistance INCREASES with an increase in temperature, the material is said to have a POSITIVE TEMPERATURE COEFFICIENT.

## How does resistivity affect resistance?

Second, the cross-sectional area of the wires will affect the amount of resistance. Wider wires have a greater cross-sectional area. Water will flow through a wider pipe at a higher rate than it will flow through a narrow pipe. The conducting ability of a material is often indicated by its resistivity.

## What is the temperature coefficient of resistance?

The resistance-change factor per degree Celsius of temperature change is called the temperature coefficient of resistance. This factor is represented by the Greek lower-case letter “alpha” (α). A positive coefficient for a material means that its resistance increases with an increase in temperature.

## What affects the resistivity?

To remove the effect of size from resistance, resistivity is used – this is a material property which does not depend on size. Restivity is affected by temperature – for most materials the resistivity increases with temperature. The ease with which a material conducts heat is measured by thermal conductivity.

## How does temperature affect the current?

An electric current flows when electrons move through a conductor, such as a metal wire. This makes it more difficult for the current to flow, and causes resistance. As the temperature increases, the metal ions vibrate more. There are more collisions with the electrons and so the resistance increases.

## What is the resistivity of a Nichrome wire?

The unit of resistivity is then ohm-meters (Ωm). Nichrome, a non-magnetic alloy that is commonly made up of 80% nickel and 20% chromium, has a resistivity ranging from 1.10 × 10−6 Ωm to 1.50 × 10−6 Ωm (0.00000110 Ωm to 0.00000150 Ωm) and a very high boiling point (~1400 °C).

## What is the difference between voltage and current?

The three basic principles for this tutorial can be explained using electrons, or more specifically, the charge they create: Voltage is the difference in charge between two points. Current is the rate at which charge is flowing. Resistance is a material’s tendency to resist the flow of charge (current).

## How does resistance change with temperature?

Surely, upon an increase in temperature, the atoms within the thermistor would vibrate with more energy and therefore more vigorously, hence making the electrons flowing through the electric circuit more likely to collide with one of the atoms, so increasing resistance.

## What is the definition of specific resistance?

Specific Resistance is the inherent property of a material… It is defined as “ the resistance offered per unit length and unit cross sectional area of that material when a known quantity of voltage is applied at its end”… Mathematically specific resistance is given by, p=(RA)/L.

## What does the resistivity of a material depend on?

The resistivity of a material is the resistance of a wire of that material of unit length and unit cross-sectional area. The unit for resistivity is the ohm-metre. The resistivity of a material depends on its nature and the temperature of the conductor, but not on its shape and size.

## How do you measure resistance?

Method 1 Measuring Resistance with a Digital Multimeter

• Choose the item whose resistance you wish to measure.
• Plug the test leads into the correct test sockets.
• Turn on the multimeter and select the best testing range.
• Touch the multimeter leads to the ends of the component you are testing.
• Turn off the multimeter.
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