Electricity Flashcards

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1
Q

What is Resistance measured in?

A

It is measured in Ohms. (symbol: Ω)

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2
Q

Define Resistance simply -

A

It is a measure of the difficulty of making current pass through the component.

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3
Q

How would you find Resistance using Voltage and Current?

A

Resistance = Voltage/Current (R = V/I)

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4
Q

What does one Ohm (symbol: Ω) represent?

A

It represents one Volt (symbol: V) per Ampere. (symbol: A)

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5
Q

Define Ohm’s Law -

A

The PD across a metallic conductor is proportional to the current through it, provided the physical conditions do not change.

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6
Q

Describe the voltage/current graph of a Resistor -

A

The graph is a straight line through the origin, the PD across the Resistor is proportional to the Current. The gradient is the resistance of the resistor.

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7
Q

What is the equation for Resistivity?

A

Resistivity, p = RA/L, where R = Resistance, L = Length and A = Cross-Sectional Area.

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8
Q

What is the unit for Resistivity?

A

The unit of resistivity is the Ohm Meter (symbol: Ωm)

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9
Q

How would you determine the Resistivity of a wire?

A

Measure the diameter of wire (d) using a micrometer at several different points and calculate the Cross-Sectional Area. (A)
Measure the Resistance (R) of different lengths (L) of the wire and plot a graph of R against L.

The Resistivity = graph gradient x A.

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10
Q

Define Superconductivity -

A

The property of zero electrical resistance in some substances at very low absolute temperatures.

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11
Q

When does a superconductor lose its superconductivity?

A

When its temperature is raised above its critical temperature.

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12
Q

What are superconductors used for?

A

They are used to make high-power electromagnets that generate very strong magnetic currents.
They are used in MRI Scanners and Particle Accelerators.

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13
Q

If components are in series, is the current entering a component the same or different to the current leaving the component?

A

It is the same.

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