SS3 First Term Physics Lesson Note – Electric Measurement

The content is just an excerpt from the complete note for SS3 First Term Physics Lesson Note – Electric Measurement. Check below to download the complete DOCUMENT

WEEK 6

ELECTRIC MEASUREMENT

CONTENT

• Resistivity and conductivity
• Conversion of galvanometer to ammeter and voltmeter
• Measuring resistance ammeter- voltmeter method.

RESISTIVITY AND CONDUCTIVITY

The resistance of a wire maintain at a constant temperature is related to its length L and its cross-sectional area (A) by the expression

R = ρl/A

Where ρ is a constant known as resistivity of the material (its unit is ohm-metre, Ωm)

ρ = RA/l

R = resistance, A = cross-sectional area, l = length of the wire.

The resistance is the ability of a material to oppose the flow of current through it.  The greater the resistivity of a wire the poorer it is as an electrical conductor. That is why conductivity is used to specify the current –carrying ability of a material.  The greater the conductivity of a material, the more easily can current flow through the material.  Hence, materials with high conductivity will have low resistively.

Conductivity, σ is the reciprocal of the resistivity

σ = 1/ρ

Electrical Conductivity:  This is a measure of the extent to which a material will allow current to flow easily through it when a p.d is applied at a specified temperature.  It is the reciprocal of the resistivity.

GALVANOMETER CONVERSION

Conversion of galvanometer to ammeter (Shunt)

To gain full access to the note: DOWNLOAD FILE