Chapter 5 - The Material World Flashcards
What is electricity?
The movement of electrons from one body to another.
Can protons move out of the nucleus of an atom?
No, only electrons can move from one atom to another.
What does it mean if an object is positively charged?
It has lost electrons and has more protons than electrons.
What does it mean if an object is negatively charged?
It has gained electrons and has more electrons than protons.
What is the unit of measurement for electrical charge?
Coulomb (C). One Coulomb is equal to 6.25×10^18 electrons or protons.
State the Law of Electrical Attraction and Repulsion.
Like charges repel, and opposite charges attract.
What is static electricity?
The movement of electrons between objects at rest (not connected in an electrical circuit).
What are three ways to charge an object at rest?
Friction, conduction, and induction.
What happens when two objects are charged by friction?
Electrons are transferred, leaving one object positively charged and the other negatively charged.
How does the electrostatic series determine charge?
It ranks materials by how strongly they hold electrons. Materials with a stronger hold become negatively charged when rubbed.
What is an electrical field?
An area of space where the electrical force of a charged object can act on another charged object.
State Coulomb’s Law.
The electrical force between two charged objects depends on their charges and the distance between them. F_e = k * (q1 * q2) / r^2.
What two factors affect the force between two charges?
The strength of the charges and the distance between them.
If the distance between two charged particles is halved, how is the force affected?
The force is quadrupled, as it is inversely proportional to the square of the distance.
What is dynamic electricity?
The flow of electrons in a circuit.
In which direction do electrons flow in a circuit?
From the positive side of the battery to the negative side.
What is current intensity?
The number of charges that pass a given point in a circuit per second.
What is the unit of current intensity?
Amperes (A).
What device is used to measure current intensity?
Ammeter, which is connected in series.
What is the formula for current intensity?
I = q / Δt
I = current (A), q = charge (C), Δt = time (s)
What is potential difference?
The difference in energy between two points in a circuit.
What is the unit of potential difference?
Volts (V).
What device is used to measure voltage?
Voltmeter, which is connected in parallel.
What is the formula for potential difference?
V = E / q
V = voltage (V), E = energy transferred (J), q = charge (C)
What is resistance?
The ability of a material to resist the flow of current.
What is the unit of resistance?
Ohms (Ω).
What happens when resistance increases in a circuit?
More energy is needed to push the current through (higher voltage required).
What is the formula for Ohm’s Law?
V = I × R
V = voltage (V), I = current (A), R = resistance (Ω)
What are the four factors that affect resistance?
- Nature of substance (conductor vs. insulator)
- Length of wire (shorter = less resistance)
- Diameter of wire (larger = less resistance)
- Temperature of wire (colder = less resistance)
What is conductance?
The ability of electric charge to flow through a path (opposite of resistance).
What is the unit of conductance?
Siemens (S).
How does current intensity change when voltage increases in a circuit with constant resistance?
Current intensity increases (directly proportional).
What happens to voltage if resistance increases but current stays the same?
Voltage increases.
What is electrical power?
The amount of energy a device transforms in a certain amount of time.
What is the unit of electrical power?
Watts (W).
What is the formula for power?
P = I × V
P = power (W), I = current (A), V = voltage (V)
What is the unit of electrical energy?
Joules (J) or kilowatt-hours (kWh).
What is the conversion factor between kWh and J?
1 kWh = 3,600,000 J.
What is the formula for electrical energy?
E = P × Δt
E = energy (J), P = power (W), Δt = time (s)
What is a series circuit?
A circuit where electrons only have one path to follow.
What is a parallel circuit?
A circuit where electrons have more than one path to follow.
What happens to total resistance in a series circuit?
It is the sum of all individual resistances.
What happens to total resistance in a parallel circuit?
It is the reciprocal sum of individual resistances.
What does Kirchhoff’s Current Law (KCL) state?
The sum of currents entering a junction equals the sum of currents leaving the junction.
What does Kirchhoff’s Voltage Law (KVL) state?
The sum of the voltage drops across resistors equals the sum of the voltage rises (from a battery) in a closed loop.
How does current behave in a series circuit?
It stays the same throughout the circuit.
How does voltage behave in a series circuit?
It adds up: V_t = V_1 + V_2 + V_3.
How does current behave in a parallel circuit?
It adds up: I_t = I_1 + I_2 + I_3.
How does voltage behave in a parallel circuit?
It stays the same: V_t = V_1 = V_2 = V_3.
