Questions and Answers
What is electric current defined as?
What is the direction of conventional current?
What is Ampere a measure of?
Which of the following is NOT a characteristic of electric current?
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What is one condition required to produce electric current?
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What is the equivalent unit for quantity of charge?
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Which device is used to measure electric current intensity?
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If a current intensity of 3.2 A passes through a conductor for 3 seconds, how many electrons pass across its cross-section? (Charge of an electron is $1.6 \times 10^{-19}$ coulombs)
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Which of the following formulas represents the relationship between charge, number of electrons, and charge of an electron?
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What is the charge of an electron?
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Study Notes
Electric Current
- Electric current is the flow of electric charges through a conductor, requiring a potential difference between its terminals.
Direction of Electric Current
- Conventional Current: Defined as the flow of positive charges from positive (+) to negative (-) pole; this direction is used throughout the syllabus.
- Electronic Current: Refers to the flow of electrons from negative (-) to positive (+) terminal.
Conditions for Electric Current
- An electric source is needed to create a potential difference between two terminals of a conductor.
- A closed circuit allows for the continuous flow of electric current.
Characteristics of Electric Current
- Electric Current Intensity (I): Measured in Amperes (A), calculated as the quantity of electric charges (Q) passing through a cross-sectional area per second.
- Electric Potential Difference (P.D): The difference in electric potential between two points in a circuit.
- Electrical Resistance (R): The opposition to the flow of electric current in a conductor.
Key Formulas
- Current intensity is calculated using the formula:
[ I = \frac{Q}{t} ]
Where Q is the quantity of charges in coulombs, and t is the time in seconds. - Rearranged, this means:
[ Q = I \times t ]
Ampere Defined
- An Ampere is the current intensity produced by the passage of one coulomb of charge through a conductor in one second.
Charge Relationships
- Charge of Electron (e): ( e = 1.6 \times 10^{-19} ) coulombs.
- Relationship between number of electrons (n) and charge:
[ Q = n \times e ]
Measurement of Current
- Electric current intensity is measured using an Ammeter, which is connected in series within the circuit.
Example Problems
-
Problem 1: With a current intensity of 3.2 A over 3 seconds:
[ Q = I \times t = 3.2 , A \times 3 , s = n \times 1.6 \times 10^{-19} ]
Results in ( n = 6 \times 10^{19} ) electrons. -
Problem 2: For an electron rotating around a hydrogen nucleus at 6.6 x ( 10^{15} ) revolutions per second:
[ I = 6.6 \times 10^{15} \times 1.6 \times 10^{-19} = 10.56 \times 10^{-14} , A ] -
Problem 3: For flow rates of electrons in wires:
Wire X: ( 10^{20} ) electrons/sec; Wire Y: ( 2 \times 10^{20} ) electrons/sec.
Results in a current intensity ratio ( \frac{I_x}{I_y} = \frac{1}{2} ).
Additional Calculation Example
- Problem 4: Based on the Bohr model, an electron moves in a circular path with a radius of 0.53 A0 and a speed of ( 2.2 \times 10^{6} , m/s ); calculation of the current intensity resulting from this motion is required.
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Description
Explore the fundamentals of electric current, including its definition and the two types: conventional and electronic. Understand the conditions necessary to obtain electric current and the significance of potential difference in conductors.
