core 3 - p1 Flashcards
(20 cards)
What are the three main particles in an atom, and what are their charges?
Electrons (negative), protons (positive), and neutrons (neutral).
Which particle is responsible for electrical current in conductors?
Electrons (they flow through conductors).
What is the SI unit of electrical charge?
Coulomb (C).
How many electron charges make up 1 Coulomb?
6.25×10 ^ 18 electrons.
What is the charge of a single electron in Coulombs?
−1.6×10 ^ −19 C.
Define electric current and its SI unit.
Current is the flow of electrons through a conductor. Unit: Ampere (A).
How is 1 Ampere defined in terms of Coulombs and seconds?
1A = 1C/s (1 Coulomb of charge passing per second).
Why is the symbol for current “I”?
Derived from the historical term “Intensity” of charge flow.
What is the difference between conventional current flow and electron flow?
Conventional current assumes flow from positive to negative; electrons actually flow from negative to positive.
Why does conventional current flow from positive to negative despite electrons moving the opposite way
Early scientists (e.g., Franklin) incorrectly assumed positive charge carriers; the convention remains for consistency.
What is electromotive force (EMF), and what is its unit?
EMF is the energy per unit charge supplied by a source (e.g., battery). Unit: Volt (V).
Is EMF actually a force? Explain.
No—it’s a potential energy difference, not a mechanical force.
How does EMF relate to energy transfer in a circuit?
EMF represents the total energy provided to move charge through a circuit.
Define potential difference and how it is measured.
Potential difference (voltage) is the energy per unit charge between two points. Measured with a voltmeter in parallel.
What instrument measures potential difference, and how is it connected in a circuit?
A voltmeter, connected in parallel to the component.
Define electrical resistance and state its SI unit.
Resistance is the opposition to current flow. Unit: Ohm ( Ω ).
According to Ohm’s Law, what is the relationship between voltage, current, and resistance?
V = I × R (Voltage = Current × Resistance).
What three factors determine the resistance of a conductor?
Resistivity (ρ), length (l), and cross-sectional area (A) : R = ρl / A.
Differentiate between resistance and resistivity.
Resistance is a property of a specific object; resistivity is a material property ( unit : Ω ⋅ m).
Write the formula for the resistance of a material given its resistivity, length, and cross-sectional area.
R= ρl / A .
