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Questions and Answers
What does a voltmeter measure?
What does a voltmeter measure?
- Potential difference between two points (correct)
- Resistance in a conductor
- Current flowing through a circuit
- Electrical energy consumed
When electric cells are connected in series, what happens to their e.m.f.s?
When electric cells are connected in series, what happens to their e.m.f.s?
- They remain the same
- They divide equally
- They add up (correct)
- They cancel each other out
What unit is used to measure potential difference?
What unit is used to measure potential difference?
- Ohm
- Coulomb
- Watt
- Volt (correct)
Which material has the lowest electrical resistance?
Which material has the lowest electrical resistance?
What happens in an open circuit?
What happens in an open circuit?
What is a function of a switch in a circuit?
What is a function of a switch in a circuit?
What is the effect of resistance on electric current in a conductor?
What is the effect of resistance on electric current in a conductor?
What results from the collision of electrons with particles in a conductor?
What results from the collision of electrons with particles in a conductor?
Which of the following best describes a series circuit?
Which of the following best describes a series circuit?
How is the precision of a voltmeter reading determined?
How is the precision of a voltmeter reading determined?
What occurs in a parallel circuit when one component fails?
What occurs in a parallel circuit when one component fails?
When electric cells are connected in a circuit, what do they form?
When electric cells are connected in a circuit, what do they form?
Which of the following can be classified as electrical insulators?
Which of the following can be classified as electrical insulators?
What is indicated by the flow of electric charge in a circuit?
What is indicated by the flow of electric charge in a circuit?
What happens when a single bulb in a series circuit is removed?
What happens when a single bulb in a series circuit is removed?
Which statement is true about circuit diagrams?
Which statement is true about circuit diagrams?
What is a serious consequence of damaged insulation on wires connected to an electric motor?
What is a serious consequence of damaged insulation on wires connected to an electric motor?
What happens when a fuse blows?
What happens when a fuse blows?
What is the relationship between the total potential difference and the individual potential differences in a series circuit?
What is the relationship between the total potential difference and the individual potential differences in a series circuit?
Which type of device is a circuit breaker classified as?
Which type of device is a circuit breaker classified as?
In a parallel circuit, how does the current behave at a junction?
In a parallel circuit, how does the current behave at a junction?
What does the e.m.f. of a cell equal in a purely parallel circuit?
What does the e.m.f. of a cell equal in a purely parallel circuit?
Which rated fuse is appropriate for an appliance that uses a 4 A current?
Which rated fuse is appropriate for an appliance that uses a 4 A current?
Which formula correctly represents the effective resistance in a series circuit?
Which formula correctly represents the effective resistance in a series circuit?
Why is it important to fit switches to the live wire of an appliance?
Why is it important to fit switches to the live wire of an appliance?
If the ammeter reading is 2.0 A in a parallel circuit, what can be said about the individual ammeter readings in the branches?
If the ammeter reading is 2.0 A in a parallel circuit, what can be said about the individual ammeter readings in the branches?
What is the role of earthing in home circuitries?
What is the role of earthing in home circuitries?
Which equation accurately describes the voltage in a series circuit?
Which equation accurately describes the voltage in a series circuit?
What should you avoid when using electrical appliances after bathing?
What should you avoid when using electrical appliances after bathing?
In what way does double insulation enhance safety?
In what way does double insulation enhance safety?
What is the effective resistance formula for two components in parallel, R1 and R2?
What is the effective resistance formula for two components in parallel, R1 and R2?
Which condition is true for the potential differences in a parallel circuit with only those components connected?
Which condition is true for the potential differences in a parallel circuit with only those components connected?
What does double insulation in electrical appliances primarily protect against?
What does double insulation in electrical appliances primarily protect against?
What is a primary characteristic of appliances that utilize double insulation?
What is a primary characteristic of appliances that utilize double insulation?
How does aluminium contribute to the safety of airplanes during lightning strikes?
How does aluminium contribute to the safety of airplanes during lightning strikes?
What does the FAA regulation ensure regarding airplane protection?
What does the FAA regulation ensure regarding airplane protection?
When lightning strikes an airplane, what typically happens to the current?
When lightning strikes an airplane, what typically happens to the current?
What is the rating of the toaster's power mentioned?
What is the rating of the toaster's power mentioned?
What is a potential risk to airplanes from lightning strikes, despite their protective measures?
What is a potential risk to airplanes from lightning strikes, despite their protective measures?
What type of wiring do appliances that lack an Earth wire typically use?
What type of wiring do appliances that lack an Earth wire typically use?
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Study Notes
Electric Circuits
- Closed Circuit: Electric charge flows continuously through an uninterrupted path.
- Open Circuit: Electric charge does not flow due to a break in the circuit.
Circuit Diagrams
- Circuit diagrams simplify the representation of electrical circuits using symbols, avoiding time-consuming 3-D drawings.
- Common circuit symbols represent various electrical components.
Switches
- Switches allow circuits to be opened or closed safely, stopping or allowing electric charge flow.
- When open, electric charge flow ceases, and bulbs do not illuminate.
Electric Cells
- Electric cells store energy chemically, converting it to electrical energy when in a circuit.
- Multiple electric cells connected form a battery and can be wired in series or parallel.
Series Circuits
- Components are connected in a single continuous path; the current remains constant.
- If one component fails (e.g., a bulb), the entire circuit becomes open, stopping the flow in all components.
Parallel Circuits
- Components provide multiple paths for electric charge to flow; the current can split among branches.
- The total current is equal to the sum of the currents in individual branches.
Potential Difference and Electromotive Force (e.m.f.)
- In Series Circuits: Total potential difference equals the sum of potential differences across individual components.
- In Parallel Circuits: The e.m.f. is equal to the potential differences across each component.
Resistance
- Resistance measures how much a component opposes the flow of electric charge.
- A higher resistance means more difficulty for current to flow, and resistors change internal energy to heat.
Conductors and Insulators
- Conductors have low resistance (e.g., copper, silver), allowing easy current flow.
- Insulators resist electrical current, protecting against shock.
Safety Features in Home Circuitries
- Circuit Breakers: Disconnect power when large currents flow, preventing damage and fires.
- Fuses: Melt and stop current flow when excessive currents occur; must be replaced after use.
- Switches: Installed on live wires to safely control device power.
Double Insulation
- Used in appliances without earth wires, ensuring insulation protects users from electric shocks.
- These devices usually have non-metallic casings.
Lightning Protection in Airplanes
- Aluminum shells of aircraft conduct electricity, allowing lightning strikes to pass through without damaging the interior.
- Aircraft components are shielded against potential lightning damage, complying with FAA regulations.
Example Problem Solving
- Calculated potential differences and resistances in circuit configurations to determine effective resistance and e.m.f. values based on series and parallel arrangements.
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