Electricity Honor

Vocational Activities

Requirements

Be able to explain and illustrate an experiment through which the laws of electrical attraction and repulsion are demonstrated.
Answer: Rub a plastic pen or PVC rod on a wool cloth: the friction makes the rod become negatively charged. Bring it close to little pieces of paper: the paper is attracted (attraction between opposite charges). Rub two rods and bring them close: they repel each other (the same charge = repulsion). Coulomb's law: like charges repel, opposite charges attract. — The law was formulated in 1785 by Charles-Augustin de Coulomb using a torsion balance — he discovered that the electrical force is proportional to the product of the charges and inversely proportional to the square of the distance (F = k·q1·q2/r²).
Explain the difference between direct and alternating current and demonstrate the uses of each. Present a method for determining which type of flow each circuit has.
Answer: Direct Current (DC): flows in a single direction, fixed polarity (+ and −). Used in cells, batteries, USB, electronics. Alternating Current (AC): reverses direction 50 or 60 times per second (50/60 Hz). Used in residential outlets and motors. To identify it: connect an LED — in DC it only lights up in one polarity; in AC it flickers so fast that it seems constantly on. — Brazil adopted a frequency of 60 Hz following the American standard due to the influence of the first foreign electric companies in the 1900s — Argentina and Europe use 50 Hz, which is why European appliances may have synchronization problems if used here.
Make a simple electromagnet, or connect a bell or lamp to a battery, using an inline switch.
Answer: Simple electromagnet: wind 1 meter of enameled copper wire around a large nail (50-100 turns), remove the enamel from the ends with sandpaper and connect each end to a pole of a 1.5V cell or 9V battery. The nail attracts paper clips and screws while the current passes. For the circuit with a lamp: battery + switch + 3V LED lamp in series; when you turn on the switch, the lamp lights up. — The electromagnet was invented by William Sturgeon in 1825 — the number of turns in the winding (coils) determines the strength of the magnetic field generated, a principle exploited by appliances such as fans and washing machines to this day.
Assemble and get a simple electric motor running, from a kit, or disassemble an electric motor and identify the parts and explain how they work.
Answer: Main parts: stator (the fixed part, contains permanent magnets or external coils that create a magnetic field), rotor (the part that spins, with coils that receive current), commutator (a segmented ring on the shaft that reverses the direction of the current every half turn), brushes (carbon contacts that carry the current from the battery to the commutator). — The electric motor was invented by Michael Faraday in 1821 — his discovery that a current in a conductive wire under a magnetic field generates mechanical motion revolutionized industry, being the basis of modern electric car motors such as Tesla and BYD.
Be able to build an electric battery.
Answer: Lemon battery: stick a galvanized (zinc) screw and a copper coin (or thick copper wire) into a lemon, without them touching. Connect a voltmeter: it generates about 0.9 V. In series, several lemons light an LED. Principle: the chemical reaction of the citric acid with the metals produces a difference in electrical potential (a principle discovered by Volta in 1800 with his original pile). — Alessandro Volta's original pile (1800) used alternating discs of zinc and copper separated by felt soaked in sulfuric acid — the modern lemon is the safe didactic version, with a milder citric acid that still works by the same electrochemical principle.
What is a fuse and what is its purpose? Demonstrate the ability to replace fuses and reset circuit breakers and show the correct way to splice electrical wires.
Answer: A fuse is a protection device that has a filament that BURNS when the current exceeds the rated value, interrupting the circuit and protecting against short circuit and overload. Replacement: turn off the circuit, remove the burnt fuse and replace it with an IDENTICAL one in amperage. Circuit breaker: a resettable device. — The fuse protects the wiring because it burns BEFORE the wiring melts — using a fuse with a higher amperage than specified nullifies the protection and can cause a fire, which is why the Brazilian NBR 5410 standard is so strict regarding the correct specification.
Show how to rescue a person in contact with electrical current and have knowledge of the first aid procedures to be adopted.
Answer: NEVER touch the electrocuted victim directly. FIRST turn off the home's main switch or circuit breaker. If you cannot turn it off, use a non-conductive object (a dry wooden broom handle, plastic) to move the victim away from the wire. Assess consciousness, breathing and pulse; if absent, begin CPR (chest compressions + breathing). Call SAMU 192 or the Fire Department 193 immediately. Do not throw water on live wires. — Residential alternating current (110/220V) causes involuntary muscle contraction — the person becomes 'stuck' to the wire unable to let go; that is why the rescuer must turn off the source first, and only then move the body away, according to the SAMU protocol.
Make a diagram of an automobile's lighting system.
Answer: Diagram: 12V battery (positive) → fuse box (protection) → relays (activation) → front headlights (high and low beam), auxiliary fog lights, front and rear lights, brake light, reverse light, turn signals, cabin interior light. The negative is grounded to the vehicle's chassis. The switches are on the dashboard and on the steering column (lever). — The 12V system was standardized in the 1950s, replacing the 6V of older vehicles — the higher voltage reduced the thickness of the wires, saving weight and cost, a standard that continues to this day in common commercial cars and motorcycles.
Make a diagram showing how lamps, switches and outlets are controlled by each fuse or circuit breaker in a house.
Answer: Diagram: utility energy meter → service entrance → distribution board with an RCD (Residual Current Device) → individual circuit breakers per circuit. Typically: 1 breaker for lighting per area (living room, bedrooms, kitchen), 1 breaker for common outlets per area, and dedicated breakers for the electric shower heater, air conditioning and washing machine. — The NBR 5410 standard requires an RCD (Residual Current Device) in all circuits of wet areas (bathrooms, kitchen, laundry area) — it detects current leakage in milliseconds and shuts off the circuit, preventing fatal shocks.
Read an electricity meter correctly and calculate a home's energy bill with the rates charged in your region.
Answer: The meter measures in kWh (kilowatt-hour). Note the current reading and the previous month's; subtract to get the consumption for the period. Example: previous reading 5,230 kWh, current 5,450 kWh → consumption 220 kWh. Multiply by the value of the kWh in your region (in Brazil ~R$0.90 to R$1.20 depending on the distributor) and add taxes (ICMS, PIS, COFINS) and the public lighting fee. — ANEEL's tariff flag (green, yellow, red 1 and 2) changes the price of the kWh by up to R$0.07 according to the situation of the hydroelectric reservoirs — visible in the upper corner of the monthly bill and directly impacting the Brazilian consumer.
What is the relationship between the intensity and the voltage of an electrical current described in Ohm's law?
Answer: Ohm's law states that the intensity of the current (I, in amperes) is directly proportional to the applied voltage (V, in volts) and inversely proportional to the resistance (R, in ohms) of the circuit. Formula: V = R · I (or I = V/R). For example, in a resistance of 10 Ω subjected to 20 V, 2 A of current pass. — Georg Ohm published the law in 1827 after experiments with wires of different lengths and materials — initially his discovery was rejected by the German community, and he was only recognized at the Royal Society of London in 1841.
Demonstrate how to use a test light and what safety measures must be taken when handling an electrical network.
Answer: The test light (neon screwdriver or multimeter) detects the presence of voltage. To use it: hold it by the insulated handle, touch the tip to the wire or outlet, observe the neon LED — it lights up when there is voltage. Safety: turn off the circuit breaker before any handling; use insulating gloves and rubber footwear. — The NR-10 (Safety in Electricity) standard of the Ministry of Labor requires mandatory training for any work on electrical networks — non-compliance means the work is embargoed and the fine can be jointly shared with the contracting company in the event of an accident.
What is the difference between a Watt and a Volt?
Answer: Volt (V) is the unit of VOLTAGE or difference in electrical potential — it represents the 'pressure' that pushes the current through the wires. Watt (W) is the unit of POWER — it represents the amount of work or energy consumed per second. Relationship: P (W) = V (V) × I (A). Examples: a residential outlet 110V or 220V; a shower heater 5500W; an LED lamp 9W. — The names are tributes: Volt comes from Alessandro Volta (Italian, inventor of the pile in 1800) and Watt comes from James Watt (Scottish, inventor of the modern steam engine in 1769) — a convention of the International System of Units.
Explain what the Joule effect or thermal effect is.
Answer: The Joule Effect (or thermal effect) is the transformation of electrical energy into heat when a current passes through a conductor with resistance. The formula is Q = I² · R · t (heat = current squared × resistance × time). Useful applications: electric shower heater, clothes iron, hair dryer, heater, fuse (it burns on purpose). — James Prescott Joule discovered the effect in 1841 — his experiment with wires immersed in water demonstrated that the heat generated is exactly proportional to the square of the current, a principle that defines the energy efficiency of any electrical system to this day.