RP4 - I-V Characteristics Flashcards

1
Q

Outline the basic steps of the practical.

A
  1. Set-up circuit with lamp/resistor/diode
  2. Alter the potential difference in regular increments
  3. Record the current for each p.d
  4. Plot a graph of current against p.d
  5. Repeat for the other two components
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2
Q

What two types of meters are needed in the circuit, and how should they be connected?

A
  1. Voltmeter: Connected in parallel to the component
  2. Ammeter: Connected in series with the component
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3
Q

What component is required to alter potential difference if you’re not using a variable power pack?

A

A rheostat, or variable resistor.

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4
Q

What is an ‘Ohmic Conductor’? State the condition required.

A

● A conductor for which current and potential difference are directly proportional
● Resistance remains constant as current changes
● Temperature must be constant

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5
Q

What specific type of ammeter may be required in this experiment and why?

A

A milliammeter since the current changes involved may be quite low.

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6
Q

What must also be present in the circuit when the diode is being tested? Where should it be connected?

A

A protective resistor should be connected to prevent the current levels getting too high. It should be connected in series with the diode.

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7
Q

For which component does the polarity of the power supply matter and why?

A

The diode, since diodes only allow current to flow through in one direction.

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8
Q

What must be kept constant to get reliable results? How can you achieve this?

A

Temperature should remain constant so that the resistance of the components isn’t affected. You should disconnect the supply when not taking readings to avoid unnecessary heating.

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9
Q

How do you determine the resistance of a component from an I-V graph?

A
  • The resistance at a given point, is the inverse of the gradient of the line drawn from that point to the origin.
  • Work out the gradient and use 1/gradient to obtain the resistance.
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10
Q

WILL BE WRITTEN ON PAPER:

What would you expect the I-V graph of a resistor to look like?

A

I is Directly Proportional to V. So staight horizontal line in the middle of I and V

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11
Q

WILL BE WRITTEN ON PAPER:

What would you expect the I-V graph of a diode to look like?

A

The line would be horizontal across the x axis in the I-V graph but ventually it will have a sudden rise in the upper right quart.

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12
Q

WILL BE WRITTEN ON PAPER:

What would you expect the I-V graph of a lamp to look like?

A

In the I-V graph it will be and S like shape.

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13
Q

What happens to the resistance of a filament lamp as the temperature increases? Why?

A

● Resistance increases
● Ions in metal have more energy, so vibrate more, causing more collisions with electrons as they flow through the metal, creating greater resistance to current flow

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