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Electricity > Current > Flashcards

Current Flashcards

1
Q

What is electric current?

A

Denoted by (I) and measured in amps (A), it is a flow of electrons.

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2
Q

What are the two types of current?

A
  • Direct current (d.c.)
  • Alternating current (a.c.)
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3
Q

What is direct current?

A

d.c. is the type of current that flows from cells and batteries. It can flow in one direction only.

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4
Q

What is alternating current?

A

a.c. is the type of current supplied by mains electricity. It alternates one way then another as it is produced. In the case of mains, it changes direction every 1/100 of a second. It has a frequency of 50Hz.

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5
Q

What are the two types of circuits?

A
  • Seires circuit
  • Parallel circuit
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6
Q

What is a series circuit?

A

A circuit in which components are connected one after the other. The current will always be the same in a series circuit.

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7
Q

What is a parallel circuit?

A

A circuit on which components are connected through parallel branches. The current splits in the individual branches.

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8
Q

The total current entering a junction of paths…

A

…will be equal to the total current exiting the junction of paths.

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9
Q

How is current measured?

A

With an ammeter placed in series.

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10
Q

What are the effects of current?

A
  • Magnetic effect
  • Chemical effect
  • Heating effect
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11
Q

What is the magnetic effect?

A

The movement of charged particles in the wire disrupts a magnetic field.

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12
Q

What is the chemical effect?

A

This can be seen when two ends of a circuit are placed in an electrolyte solution. Gas bubbles are produced as chemical reactions take place.

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13
Q

What is the heating effect?

A

Current produces heat. This can be seen in kettles and devices heating up after a long use. This is probably the most important effect in relation to the practical use of electricity.

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14
Q

What can happen due to the heating effect?

A
  • Energy can be lost in electrical transmission through heat loss
  • Electrical circuits have to be designed and monitored to avoid fire or melting due to overheating
  • Current can be used to heat objects
  • Light can be emitted from objects that are heated
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15
Q

State Joule’s law.

A

The rate of heat produced in a constant resistance conductor is proportional to the square of the current.

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16
Q

How would you demonstrate the magnetic effect?

A

Set up a circuit with a power source and switch, place a compass over the wire, watch the needle deflect as the circuit is turned on and off.

17
Q

How would you demonstrate the chemical effect?

A

Set up a circuit with a power source, rheostat, switch and copper and iron plates in a copper sulphate electrolyte solution, the solution will bubble when the circuit is on.

18
Q

How would you demonstrate the heating effect?

A

Set up a circuit with a power source, switch, rheostat, heating coil, calorimeter and thermometer, the temperature will rise proportionally to the square of the current applied.

19
Q

What is the chemical effect of current also known as?

A

Electroplating

20
Q

What can electroplating/electrodisposition be used for?

A
  • Protection
  • Aesthetics
  • Circuit building
21
Q

What are the materials we look at the effects of current and voltage for?

A
  • Metallic conductor
  • Filament bulb
  • Semiconductor (thermistor)
  • Electrolyte solution
  • Vacuum
  • Gas
22
Q

What is the effect of current and voltage on a metallic conductor?

A

A metallic conductor obeys Ohm’s law. Voltage is directly proportional to current at constant temperature.

23
Q

What is the effect of current and voltage on a filament bulb?

A

The filament bulb gets hotter as current flows. This increases resistance and the current tends to drop off slightly as voltage is increased.

24
Q

What is the effect of current and voltage on a semiconductor (thermistor)?

A

When voltage is applied current increases and the semiconductor heats up.

25
Q

What is the effect of current and voltage on an electrolyte solution with active electrodes?

A

Obeys Ohm’s law, current is directly proportional to voltage. Straight line through the origin.

26
Q

What is the effect of current and voltage on an electrolye solution with inactive electrodes?

A

Behave as a cell with an emf across the electrodes. Until the applied voltage exceeds this emf, no current flows. Directly proportional, straight line but not through the origin.

27
Q

What is the effect of current and voltage on a vacuum?

A

Current stars off increasing with voltage, but evens out and constant current flows. (Thermionic emission)

28
Q

What is the effect of current and voltage on gas?

A

Current starts off increasing with voltage, evens out but after a while will start increasing again.

Electricity (11 decks)

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