Current, voltage and resistance：練習問題

A student connects a battery, a switch, and a light bulb in a single loop. When the switch is closed, the bulb lights up. What type of circuit is this?

If the current in the main loop of a parallel circuit is measured as \(3\,A\) and one branch has a current of \(1\,A\), what is the current in the other branch (assuming only two branches exist)?

Two conductors, Wire P and Wire Q, are made of the same material and are connected one at a time across the terminals of an identical battery (constant voltage, V). Wire P has a length of L and a cross-sectional area of A. Wire Q has a length of 3L and a cross-sectional area of rac{A}{3}. If the current measured in Wire P is IP, what is the current IQ flowing through Wire Q?

Which of the following is the standard unit used to measure voltage in an electrical circuit?

In a simple electrical circuit consisting of a battery and a piece of nichrome wire, a student wants to increase the electric current flowing through the circuit. Which of the following changes to the wire would achieve this goal?

What is the function of a voltmeter in an electrical circuit, and how is it connected to measure voltage across a component?

If you connect a battery with greater voltage to a circuit, how would it affect the current flowing through the circuit, assuming the circuit's resistance remains unchanged?

A student observes that when a battery is connected to a long, thin copper wire, a small current flows. If the student replaces this wire with a short, thick aluminium wire of the same length as the original, what changes in resistance and current would likely be observed, assuming aluminium has higher resistivity than copper? Justify your answer by considering relevant factors affecting resistance.

(a) What instrument should be used to measure electric current, and how is it connected in an electrical circuit (in series or in parallel with the component)?

(b) What instrument should be used to measure voltage, and how is it connected in an electrical circuit (in series or in parallel with the component)?

(c) A simple lamp has an electrical resistance of $$15 \, \Omega$$. If a current of $$0.4 \, A$$ flows through it, calculate the voltage supplied by the battery. Show your formula and calculation.

(d) If the voltage from the battery is kept constant but the lamp is replaced with one having higher resistance, what would happen to the current flowing through the circuit? Explain your answer with reference to Ohm's Law.

(a) Identify two primary physical factors (excluding temperature) that affect the electrical resistance of a metallic wire. Explain how each factor influences resistance.

(b) Wire X is made of copper, 1 meter long, with a cross-sectional area of $$2 \, \text{mm}^2$$. Wire Y is made of nichrome (a material with higher resistivity than copper), 1 meter long, with a cross-sectional area of $$1 \, \text{mm}^2$$. Which wire would have a higher electrical resistance? Explain your reasoning based on the factors affecting resistance.

(c) Both Wire X and Wire Y are connected separately to identical 5 V batteries. Which wire would allow a larger current to flow through it? Justify your answer using Ohm's Law.

(d) If Wire X has a resistance of $$0.1 \, \Omega$$, calculate the power dissipated by Wire X when it is connected to the 5 V battery. Show your formula and calculation.