Electricity: Charge, Fields, and Circuits
Charge and Electric Fields
Electrostatics
Electric charge comes in positive and negative types. Like charges repel and opposite charges attract. The electric field describes the force per unit positive test charge: .
What does electric field represent?
Electric field is defined as force per unit positive test charge.
Correct answer: Force per unit charge
What is the difference between current and charge?
Charge is the quantity of electricity, while current is the rate at which charge moves: .
Correct answer: Current is charge flow rate
Potential Difference and Circuits
Voltage and resistance
Potential difference measures energy change per unit charge. In many materials, Ohm’s law applies: . Resistance depends on geometry and material properties.
Circuit terms
Safety note
Electric shock risk depends on current through the body, path, and duration, not just voltage alone.
In a simple resistor, what happens if voltage increases while resistance stays constant?
From , current increases proportionally with voltage when is constant.
Correct answer: Current increases
Why are conductors useful in circuits?
Low resistance materials make it easier to deliver energy and signals efficiently.
Correct answer: They allow charge to flow easily
Practical applications
Electrical systems power lighting, motors, sensors, and communication devices. Understanding fields and circuits helps with energy efficiency, control, and safety.
Which quantity is measured in amperes?
The ampere is the SI unit of electric current.
Correct answer: Current