Current Electricity Flashcards
What is the difference between electromotive force (emf), potential difference (p.d.), current, and internal resistance of a cell?
Emf: The total energy provided by a cell or battery per coulomb of charge.
Potential Difference (p.d.): The energy difference between two points in a circuit.
Current: The flow of electric charge through a conductor, measured in amperes (A).
Internal Resistance: The resistance within the cell that causes some energy to be lost as heat.
What is Ohm’s law?
Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance of the conductor.
How do you calculate the effective total resistance of resistors in series and parallel?
Series: The total resistance
𝑅_𝑡𝑜𝑡𝑎𝑙
is the sum of all resistances
𝑅_𝑡𝑜𝑡𝑎𝑙 = 𝑅₁ + 𝑅₂ + ⋯ + 𝑅ₙ
Parallel: The reciprocal of the total resistance 𝑅_𝑡𝑜𝑡𝑎𝑙
is the sum of the reciprocals of each resistance
1/𝑅_𝑡𝑜𝑡𝑎𝑙 = 1/𝑅₁ + 1/𝑅₂ + ⋯ + 1/𝑅_ₙ
What is the potentiometer and how is it used to measure emf, current, and internal resistance?
A potentiometer is a device used to measure the emf of a cell, the internal resistance, and current without drawing any current from the circuit. It does this by comparing the unknown emf with a known voltage.
What are the advantages of using a potentiometer over a voltmeter?
A potentiometer provides more accurate measurements because it doesn’t draw current from the circuit, thus avoiding the error of “lost volts.”
It can measure very small potential differences with high precision.
How is Kirchhoff’s law applied in electrical networks?
Kirchhoff’s Current Law (KCL): The total current entering a junction equals the total current leaving the junction.
Kirchhoff’s Voltage Law (KVL): The sum of all electromotive forces and potential differences around any closed loop in a circuit equals zero. These laws are used to analyze complex electrical circuits and determine the current and voltage in each component.
How can you determine the resistivity and conductivity of a conductor?
Resistivity 𝜌 = 𝑅𝐴 / 𝐿
where 𝑅 is the resistance,
𝐴 is the cross-sectional area, and
𝐿 is the length of the conductor. Conductivity is the inverse of resistivity,
𝜎 = 1 / 𝜌
What is the formula for Ohm’s Law?
Ohm’s Law is given by the formula 𝑉 = 𝐼𝑅
where: 𝑉 is the voltage across the conductor (in volts),
𝐼 is the current through the conductor (in amperes),
𝑅 is the resistance of the conductor (in ohms).
What is the formula for the power of an electrical circuit?
The power 𝑃 in an electrical circuit is given by the formula:
𝑃 = 𝐼𝑉 where:
𝑃 is the power (in watts),
𝐼 is the current (in amperes),
𝑉 is the voltage (in volts).
Alternatively, using Ohm’s Law:
* 𝑃 = 𝐼² × 𝑅
* 𝑃 = 𝑉² / 𝑅
How do you calculate the energy stored in a capacitor?
The energy 𝐸 stored in a capacitor is given by the formula:
𝐸 = 1 / 2 𝐶𝑉²
where:
* 𝐶 is the capacitance (in farads),
* 𝑉 is the voltage across the capacitor (in volts).
Q: How do you calculate the electromotive force (emf) in a circuit with internal resistance?
The emf 𝜖 of a cell is related to the terminal voltage 𝑉, current 𝐼, and internal resistance 𝑟 by:
𝜖 = 𝑉 + 𝐼𝑟
What is the formula for calculating the potential difference using a potentiometer?
The potential difference
𝑉 measured using a potentiometer is given by:
𝑉 = 𝑘 × 𝑙
where: 𝑘 is the potential gradient,
𝑙 is the length of the wire.
What are Kirchhoff’s Laws and their formulas?
Kirchhoff’s Current Law (KCL): The sum of currents entering a junction equals the sum of currents leaving the junction:
∑ 𝐼_in = ∑ 𝐼_out
Kirchhoff’s Voltage Law (KVL): The sum of all electromotive forces and potential differences in any closed loop of a circuit equals zero:
∑ 𝑉 = 0
