Energy and voltage in circuits Flashcards
What is a series circuit?
In a series circuit, the same current flows through all components, and one switch controls all components. If one component fails, the circuit is broken (e.g., fairy lights).
What is a parallel circuit?
In a parallel circuit, each branch gets the same voltage. If one component fails, others continue working, and different branches can have separate switches.
How does current in a series circuit depend on applied voltage and components?
Current remains the same throughout the circuit. Adding resistors increases total resistance, reducing current (Ohm’s Law). Increasing voltage increases current (Ohm’s Law). More components mean voltage is shared, reducing the brightness of bulbs in a series circuit.
How does current vary with voltage in wires and resistors?
Wires and resistors obey Ohm’s Law, meaning current is directly proportional to voltage, producing a straight-line graph.
How does current vary with voltage in filament lamps?
In filament lamps, resistance increases as temperature increases, causing a curved graph (non-linear relationship).
How do diodes behave in relation to current and voltage?
Diodes allow current to flow in one direction only, blocking current in the opposite direction, with an exponential increase after threshold voltage.
What is the behavior of LEDs?
LEDs operate similarly to diodes but emit light when conducting.
How do thermistors and LDRs behave with temperature or light intensity?
Thermistors and LDRs show a curved graph depending on temperature or light intensity.
How can you investigate current-voltage characteristics experimentally?
Set up a circuit with a power supply, ammeter, voltmeter, and a variable resistor. Change the voltage and measure the current, then plot a current-voltage (I-V) graph.
What does a straight-line graph indicate in current-voltage characteristics?
A straight-line graph indicates an Ohmic conductor (constant resistance).
What does a curved graph indicate in current-voltage characteristics?
A curved graph indicates non-ohmic behavior (resistance changes with voltage).
What happens when resistance changes in a circuit?
Increasing resistance decreases current for a fixed voltage, while decreasing resistance increases current. Variable resistors control resistance, adjusting current flow.
How do LDRs behave with light intensity?
In LDRs, brighter light results in lower resistance, increasing current. They are used in automatic street lights and camera light sensors.
How do thermistors behave with temperature?
In thermistors, higher temperature results in lower resistance, increasing current. They are used in temperature sensors, central heating systems, and car engine sensors.
How do lamps and LEDs indicate the presence of current?
A lamp lights up when current flows, and LEDs emit light when current flows in the correct direction.
What is Ohm’s Law?
Ohm’s Law defines the relationship between voltage, current, and resistance. If resistance increases, current decreases (if voltage is constant).
What is the definition of electric current?
Current is the rate of flow of electric charge, measured in amperes (A). In metals, current is due to the flow of free electrons.
What is voltage in terms of energy transfer?
Voltage is the energy transferred per unit charge. A volt (V) = 1 joule per coulomb.
What is the equation for energy transferred in a circuit?
Energy transferred is given by the equation: Energy (Joules, J) = Charge (Coulombs, C) × Voltage (Volts, V).
How does a simple circuit breaker work?
A circuit breaker automatically switches off an electrical circuit if the current becomes too high. It includes an electromagnet, soft iron armature, and springs for normal operation and resetting.
What happens during overload or short circuit in a circuit breaker?
When the current in a circuit increases, the strength of the electromagnet also increases.
This pulls the soft iron armature towards the electromagnet.
As a result, Spring 1 pulls apart the contact, disconnecting the circuit immediately and stopping current flow.
The sudden disconnection prevents overheating and damage to electrical components.
What are the advantages of circuit breakers over fuses?
Circuit breakers can be reset instead of replaced, respond faster to faults, and are more reliable for protecting appliances from damage due to power surges.
Components of a Circuit Breaker:
Electromagnet: Connected to terminal B, it detects excessive current.
Soft iron armature: A movable part that is attracted by the electromagnet when current is too high.
Spring 1 (attached to the contact at Terminal A): Normally keeps the circuit closed.
Spring 2 (attached to the reset button): Allows manual resetting after the circuit is tripped.
Contacts (Terminal A & B): Connect the live wire to complete the circuit under normal conditions.
How does a simple circuit breaker work in normal conditions ?
Normal Operation:
Electricity flows through the live wire and passes through the electromagnet, which remains inactive under normal current conditions.
The soft iron armature stays in place, and the contacts remain closed, allowing current to flow.
