Electric current
12 flashcards to master Electric current
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Define electric current in terms of the flow of charge.
Electric current is the rate of flow of electric charge. It is the amount of charge passing a point in a circuit per unit time. Current is measured in Amperes (A).
A current of 3.5 A flows through a wire. State what this indicates about the amount of charge moving through the wire per second.
This indicates that 3.5 Coulombs of charge are passing through any point in the wire every second. One Ampere is equivalent to one Coulomb per second.
Describe how you would use an analogue ammeter with a range of 0-5A to measure the current flowing through a lamp in a circuit.
1. Connect the ammeter in series with the lamp.
2. Ensure the ammeter is connected with the correct polarity (+ to + and - to -).
3. Read the current value from the scale, noting the units (Amperes or A).
State two differences between using an analogue ammeter and a digital ammeter to measure current in a circuit.
1. An analogue ammeter displays the current using a needle on a scale, whereas a digital ammeter displays the current as a numerical value on a screen.
2. A digital ammeter may have autoranging capability, while an analogue ammeter requires the user to select the appropriate range manually to avoid damaging the meter or getting inaccurate readings.
Describe how electrical conduction occurs in a metal wire.
In a metal, electrons are not bound to individual atoms but are free to move throughout the metallic structure. When a potential difference (voltage) is applied across the wire, these free electrons experience an electric force, causing them to drift in a specific direction. This directed movement of free electrons constitutes an electric current.
State what particles are responsible for electrical conduction in metals.
Free electrons are responsible for electrical conduction in metals. These are electrons that are not bound to individual atoms and can move freely throughout the metal's structure.
Define the difference between direct current (d.c.) and alternating current (a.c.).
Direct current (d.c.) flows in one direction only. Alternating current (a.c.) changes direction periodically.
State one common use of direct current (d.c.) and one common use of alternating current (a.c.).
d.c.: Powering a torch or mobile phone. a.c.: Powering household appliances such as a kettle or washing machine.
Define electric current. State the equation relating current, charge, and time, defining each symbol.
Electric current is defined as the rate of flow of electric charge. It is the amount of charge passing a point per unit time.
The equation is: I = Q/t
Where:
I = current (in Amperes, A)
Q = charge (in Coulombs, C)
t = time (in seconds, s)
A charge of 6.0 C passes through a point in a circuit in 3.0 s. Calculate the electric current at that point.
I = Q/t
I = 6.0 C / 3.0 s
I = 2.0 A
The electric current is 2.0 Amperes. This is the rate at which charge is flowing through the point.
State the direction of conventional current flow in a circuit.
Conventional current flows from the positive terminal to the negative terminal.
Explain the difference between the direction of conventional current and the flow of free electrons in a copper wire within a circuit.
Conventional current is defined as flowing from positive to negative. However, free electrons, which are the charge carriers, actually flow from negative to positive. This is because electrons are negatively charged and are repelled by the negative terminal and attracted to the positive terminal.
Key Questions: Electric current
Define electric current in terms of the flow of charge.
Electric current is the rate of flow of electric charge. It is the amount of charge passing a point in a circuit per unit time. Current is measured in Amperes (A).
Define the difference between direct current (d.c.) and alternating current (a.c.).
Direct current (d.c.) flows in one direction only. Alternating current (a.c.) changes direction periodically.
Define electric current. State the equation relating current, charge, and time, defining each symbol.
Electric current is defined as the rate of flow of electric charge. It is the amount of charge passing a point per unit time.
The equation is: I = Q/t
Where:
I = current (in Amperes, A)
Q = charge (in Coulombs, C)
t = time (in seconds, s)
State the direction of conventional current flow in a circuit.
Conventional current flows from the positive terminal to the negative terminal.
About Electric current (4.2.2)
These 12 flashcards cover everything you need to know about Electric current for your Cambridge IGCSE Physics (0625) exam. Each card is designed based on the official syllabus requirements.
What You'll Learn
- 4 Definitions - Key terms and their precise meanings that examiners expect
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After mastering Electric current, explore these related topics:
- 4.2.1 Electric charge - 20 flashcards
- 4.2.3 Electromotive force and potential difference - 14 flashcards
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