Current Flashcards

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1
Q

Define the Ampere.

A

1 Ampere is 6.25x10^18 electrons passing a point every second.

(i.e. 1 A = 1 C/s)

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2
Q

What does Joule’s law state?

A

That the rate of heat produced is proportional to the square of the current (when resistance is constant).

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3
Q

What is electric current?

A

The flow of electrons.

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4
Q

Give a property of direct current.

A

It flows in ONE direction only.

Produced by cells and batteries

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5
Q

How does current flow according to conventional current?

How does current flow in reality?

A
  • Conventional: Current flows from positive to negative.

- Reality: Current flows from negative to positive.

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6
Q

Give the formula for charge (in terms of current and time).

A

Q = I x t

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7
Q

Where is an ammeter placed in a circuit when measuring current?

A

In series. This is because current is constant throughout a series circuit.

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8
Q

What are the effects of current?

A
  • Magnetic effect
  • Heating effect
  • Chemical effect
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9
Q

What is the significance of the heating effect of current?

A
  • Massive amounts of heat can be lost through energy transfer across long distances.
  • Electrical equipment can overheat/melt.
  • Current can be used for heating objects via heating elements.
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10
Q

How do you demonstrate the magnetic effect of current?

A
  • Place a compass on a wire.
  • Switch on the circuit, the compass needle deflects.
  • Switch off, returns to normal.
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11
Q

How do you demonstrate the chemical effect of current?

A
  • Connect an anode (copper) and a cathode (zinc) plate to a power supply and run a current through the circuit.
  • The copper anode dissolves and the iron cathode is coated in the copper ions.
  • This is called ‘electroplating’.
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12
Q

How do you demonstrate the heating effect of current?

A
  • Connect an insulated calorimeter to a power supply.
  • Let a current flow through the circuit and measure the temperature over a set time with a digital thermometer.
  • The current value will be proportional to the kelvin temperature.
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