Question

What happens when the student closes the switch in Circuit 1 ? (A) The light bulb lights up. (B) The iron bar becomes magnetized. (C) Nothing, because iron does not conduct electricity. (D) The iron bar becomes hot and begins to melt.

Short answer

(A) The light bulb lights up.

Step-by-step solution

Understand the properties of iron

Iron is a metal, and generally, metals are good conductors of electricity. Iron conducts electricity, so we can discard choice (C) immediately.

Analyze current flow in Circuit 1

When the student closes the switch, a closed circuit is created. In a closed circuit, current flows from the battery through the components and back to the battery. If the light bulb and the iron bar are connected in the circuit, the electric current will flow through them.

Determine the effect of current on the light bulb and the iron bar

If the electric current flows through both components, it may cause some changes in them. We'll analyze the individual components to determine their responses to the electric current. (A) Light bulb: When a light bulb is part of a closed circuit, the electric current flows through its filament, heating it and ultimately causing the bulb to emit light. So, it's reasonable for the light bulb to light up. (B) Iron bar: Magnetization of an iron bar requires a magnetic field, which usually occurs when an electric current moves through a coil of wire wrapped around the iron bar. If that's not the case in Circuit 1, then the iron bar will not become magnetized. (D) Melting iron bar: Iron has a high melting point, and the battery used in the circuit will most likely not generate enough heat to melt the iron. Additionally, if any heat is generated in the iron bar, it would typically not be enough to melt it.

Choose the correct answer

Based on the analysis of each option, the most plausible outcome when the student closes the switch in Circuit 1 is (A) The light bulb lights up.

Key concepts

Electric Circuits

Understanding electric circuits is crucial for students beginning their exploration into the world of physics and electronics. An electric circuit is a pathway, consisting of wires and other components, that allows the flow of electric current. When the switch in a circuit is closed, it completes the pathway, allowing electrons to move from the power source, such as a battery, and through the circuit.

Components in a circuit, such as light bulbs, resistors, and inductors, have specific functions. For example, a light bulb contains a filament that heats up and glows when current passes through it, providing light. On the other hand, resistors control the amount of current flowing, and inductors can store energy in a magnetic field. Teacher-facilitated demonstrations and interactive simulations can greatly help students visualize the flow of current and how components behave in a simple circuit.

Conductivity of Metals

Metals are known for their excellent electrical conductivity, meaning they allow the flow of electric charge with ease. This property is due to the structure of metallic bonds, where electrons move freely among a lattice of ions. This 'sea' of delocalized electrons can carry electric current when a potential difference is applied across the metal.

Iron, which is commonly used in educational settings, is a good conductor of electricity. Its conductivity, while not as high as copper or silver, is still sufficient to allow current to pass through with minimal resistance. When working with circuits in class, ensuring that students understand why certain materials like metals are chosen for specific components, such as wires and contacts, can solidify their grasp of material properties in electrical applications.

Magnetization

Magnetization is the process by which objects gain magnetic properties, typically when exposed to a magnetic field. In the case of an iron bar within a circuit, magnetization would occur if the iron is subjected to a consistent magnetic field, which could be produced by electric current flowing through a coil wrapped around the bar. This is the principle behind electromagnets.

However, without a coil, a simple iron bar in a circuit would generally not become magnetized simply due to the current passing through it. Understanding the relationship between electricity and magnetism, known as electromagnetism, is a foundational concept in physics. Students benefit from experiments that showcase the creation of electromagnets to observe firsthand how electric currents can produce and manipulate magnetic fields.