Chapter 8 energy power and resistance Flashcards
(13 cards)
What is Ohm’s Law?
The current through a conductor is directly proportional to the voltage across it, provided the temperature remains constant.
V=IR
What is resistance?
The opposition to the flow of electric current, measured in ohms (Ω).
What is the unit of resistance?
Ohms (Ω).
What factors affect the resistance of a conductor?
Length of the conductor (longer = more resistance), Cross-sectional area (larger = less resistance), Material (different materials have different resistivities), Temperature (higher = more resistance in most materials).
What is the equation for power in an electrical circuit?
P = IV
Where: P = power, I = current, V = voltage.
How can power be expressed in terms of resistance?
P = I²R = V²/R
What is the definition of electric current?
The rate of flow of charge: I = Q/t
Where: I = current, Q = charge, t = time.
What is the definition of potential difference (voltage)?
The energy transferred per unit charge between two points in a circuit: V = E/Q
What is the formula for calculating energy transferred in an electric circuit?
Energy = Power × Time
E = Pt.
What is the resistivity of a material?
The property of a material that determines its resistance, dependent on its composition and temperature: ρ = RA/L
What is the relationship between resistance and temperature in a thermistor?
In a negative temperature coefficient (NTC) thermistor, resistance decreases as temperature increases. In a positive temperature coefficient (PTC) thermistor, resistance increases as temperature increases.
What is the difference between a conductor and an insulator?
Conductor: Material with low resistance, allowing current to flow easily (e.g., copper). Insulator: Material with high resistance, preventing current flow (e.g., rubber).
What is a superconductor?
A material that has zero electrical resistance below a certain critical temperature.
