Define electric current .

Electric current is the rate of flow of electric charge , measured in amperes (A) , where 1 A = 1 C s -1 .

Define potential difference .

Potential difference is the electrical work done per unit charge flowing between two points, measured in volts (V) , where 1 V = 1 J C -1 .

Conventional current is defined as the flow of .......... charge, from the .......... terminal to the .......... terminal of a cell.

Conventional current is defined as the flow of positive charge, from the positive terminal to the negative terminal of a cell.

How is current measured in a circuit, and how must the meter be connected?

Current is measured using an ammeter , which must be connected in series with the component being measured.

How is potential difference measured in a circuit, and how must the meter be connected?

Potential difference is measured using a voltmeter , which must be connected in parallel with the component being measured.

For a given potential difference across a component, how does resistance affect the current that flows?

The higher the resistance, the lower the current that can flow The lower the resistance, the higher the current that can flow

True or False? Potential difference is the same thing as electrical energy.

False. Potential difference is the electrical work done per unit charge , not energy itself. Two cells can have the same potential difference but store different amounts of energy.

For a conductor at constant temperature , the current through it is proportional to the potential difference across it.

What is the shape of the I - V graph for an ohmic conductor at constant temperature?

A straight line through the origin .

How can the resistance of an ohmic conductor be found from its I - V graph?

Resistance R = 1 ÷ gradient of the graph.

The I - V graph for a filament lamp is an .......... shaped curve.

The I - V graph for a filament lamp is an 'S' shaped curve.

Why does the current in a filament lamp increase at a slower rate as potential difference increases?

As current increases, the filament's temperature increases . Since it is a metal, this causes its resistance to increase , which opposes the current and makes it rise more slowly.

Describe the I - V characteristic of a semiconductor diode in forward bias and reverse bias.

Forward bias : current increases sharply once a threshold potential difference is reached Reverse bias : current remains at zero regardless of potential difference

True or False? A filament lamp obeys Ohm's law at all voltages.

False. A filament lamp only obeys Ohm's law for small voltages , before self-heating raises its resistance and curves the I - V graph.

A LevelPhysicsAQAFlashcardsElectricityCurrent–Voltage Characteristics

Current–Voltage Characteristics (AQA A Level Physics): Flashcards

Exam code: 7408

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FrontBasics of Electricity
Define electric current.

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Cards in this collection (15)

Define electric current.
Electric current is the rate of flow of electric charge, measured in amperes (A), where 1 A = 1 C s^-1.
Define potential difference.
Potential difference is the electrical work done per unit charge flowing between two points, measured in volts (V), where 1 V = 1 J C^-1.
Conventional current is defined as the flow of .......... charge, from the .......... terminal to the .......... terminal of a cell.
Conventional current is defined as the flow of positive charge, from the positive terminal to the negative terminal of a cell.
How is current measured in a circuit, and how must the meter be connected?
Current is measured using an ammeter, which must be connected in series with the component being measured.
How is potential difference measured in a circuit, and how must the meter be connected?
Potential difference is measured using a voltmeter, which must be connected in parallel with the component being measured.
Define resistance.
Resistance is the opposition of a component to the flow of electric current through it, given by $R = \frac{V}{I}$ and measured in ohms (Ω).
For a given potential difference across a component, how does resistance affect the current that flows?
- The higher the resistance, the lower the current that can flow
- The lower the resistance, the higher the current that can flow
True or False?
Potential difference is the same thing as electrical energy.
False.
Potential difference is the electrical work done per unit charge, not energy itself. Two cells can have the same potential difference but store different amounts of energy.
Define Ohm's law.
For a conductor at constant temperature, the current through it is proportional to the potential difference across it.
What is the shape of the I-V graph for an ohmic conductor at constant temperature?
A straight line through the origin.
How can the resistance of an ohmic conductor be found from its I-V graph?
Resistance R = 1 ÷ gradient of the graph.
The I-V graph for a filament lamp is an .......... shaped curve.
The I-V graph for a filament lamp is an 'S' shaped curve.
Why does the current in a filament lamp increase at a slower rate as potential difference increases?
As current increases, the filament's temperature increases. Since it is a metal, this causes its resistance to increase, which opposes the current and makes it rise more slowly.
Describe the I-V characteristic of a semiconductor diode in forward bias and reverse bias.
- Forward bias: current increases sharply once a threshold potential difference is reached
- Reverse bias: current remains at zero regardless of potential difference
True or False?
A filament lamp obeys Ohm's law at all voltages.
False.
A filament lamp only obeys Ohm's law for small voltages, before self-heating raises its resistance and curves the I-V graph.

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