Grade 10 physics – Introduction to Electronics Quiz

Electric current is the rate of flow of charge and is measured in amperes (A). Volts measure voltage, ohms measure resistance, coulombs measure charge.

Voltage or potential difference is measured in volts (V). Amperes measure current, ohms measure resistance, watts measure power.

Ohm's law states V (voltage) = I (current) × R (resistance). Rearranged forms give I = V/R or R = V/I.

A resistor provides controlled opposition to current flow and is used to limit current. Capacitors store charge, diodes allow one-way current, LEDs emit light.

In series, resistances add: R_total = R1 + R2 + ... so the equivalent resistance is the sum of individual resistances.

Parallel connection provides additional paths for current, so the equivalent resistance is lower than the smallest individual resistor.

A capacitor stores energy in an electric field between its plates. A battery stores chemical energy, an inductor stores magnetic energy, a resistor dissipates energy as heat.

Silicon is widely used as a semiconductor in electronic devices. Copper is a conductor, glass and rubber are insulators.

LEDs are diodes and are polarised. The anode (usually longer lead) must be connected to the positive supply and the cathode to the negative to forward-bias and light the LED.

A voltmeter measures electrical potential difference (voltage). An ammeter measures current; an oscilloscope displays waveforms but basic measurement tool here is voltmeter.

An ohmmeter measures resistance in ohms. Many multimeters include an ohm measurement function.

Earthing provides a low-resistance path for fault currents to flow to ground, reducing the risk of electric shock and protecting users.

In conductors like metal wires, electrons (negatively charged) move and constitute the electric current. Protons and neutrons are bound in nuclei; photons are light quanta.

By convention, electric current direction is taken as the flow of positive charge, i.e. from positive terminal to negative terminal. Electron flow is opposite.

The right-hand thumb rule shows that if the thumb points in the direction of current, the curled fingers show the direction of the magnetic field around the wire.

Electromagnet strength increases with more turns of wire and with higher current. An iron core also increases strength compared to no core.

A diode is nonlinear: its current–voltage relationship is not proportional, so it does not obey Ohm's law. Fixed resistors approximately follow Ohm's law over a range.

A resistor in series with an LED limits current to a safe value so the LED is not damaged and the brightness is controlled.

A transistor can amplify signals or act as a switch: a small input current or voltage at its base/gate controls a larger current through collector-emitter (or drain-source).

Kenya uses mains electricity of approximately 240 volts at 50 hertz. 110–120 V is used in some other countries; 12 V is for low-voltage systems.

Copper is widely used for electrical wiring because it has very low resistance and good ductility. Wood, glass and rubber are insulators.

Electrical power P (in watts) equals voltage V times current I: P = V × I. Using Ohm's law this can also be written as P = I^2R or P = V^2/R.

A battery supplies direct current (DC), where the current flows in one direction from the positive to the negative terminal.

An electromagnet is made by winding insulated wire around an iron core (like a nail) and supplying current; the current creates a magnetic field concentrated by the iron core.

A diode is a semiconductor device that permits current flow primarily in one direction (forward bias) and blocks it in the reverse direction.

Electric current is the movement (flow) of electrons along a conductor. Protons do not move in solid metal wires, and voltage is the electric pressure rather than the flow.

Current is measured in amperes (A). Voltage is measured in volts, resistance in ohms, and power in watts.

Voltage is the potential difference or 'electric pressure' that causes charges to move. Current is the flow, and resistance opposes that flow.

Ohm's law states that voltage (V) equals current (I) multiplied by resistance (R): V = I × R.

From V = I × R, if V is constant and R doubles, current I = V/R becomes half of its original value.

For series connection, total resistance is the sum of individual resistances: R_total = R1 + R2 + ...

In a parallel circuit, current has multiple paths so the combined resistance becomes smaller than the smallest branch resistance.

A capacitor stores electrical charge on its plates. Resistors do not store charge, diodes direct current, and a speaker converts electrical signals to sound.

A diode conducts current mainly in one direction (forward) and blocks it in the reverse direction, making it useful for rectification.

An LED is a diode designed to emit visible light when a forward current flows through it. It does not store charge or increase voltage.

A transistor can control a large current with a small input signal, so it is used as a switch or amplifier in electronic circuits.

A fuse melts when excessive current flows, opening the circuit and protecting wiring and devices from damage or fire.

Kenya uses a mains supply of about 240 volts alternating current at 50 hertz. Other values are used in different countries.

A multimeter can measure voltage, current and resistance, making it a standard tool for school electronics experiments.

A short circuit bypasses the intended load with a low resistance path, causing excessive current which can damage components or cause fire.

Resistance is measured in ohms (Ω). Voltage is in volts, current in amperes, and charge in coulombs.

Copper is an excellent conductor of electricity and is widely used for electrical wiring. Wood, rubber and glass are insulators.

By convention, the longer line in the cell symbol represents the positive terminal and the shorter line the negative terminal.

Resistors are placed in series with LEDs to limit current to a safe value so the LED is not damaged.

After charging, a capacitor blocks steady DC current because no further charge flows once it reaches the applied voltage; it passes changing signals (AC).

Alternating current reverses direction many times per second (has a frequency). Mains electricity is AC.

A breadboard allows quick assembly and modification of circuits during experiments, without soldering components together.

Using Ohm's law I = V/R = 9 V ÷ 3 Ω = 3 A.

Diodes allow current in one direction and are used in rectifier stages to change AC into pulsating DC for power supplies.

Earthing directs unwanted fault currents safely to the ground so that metal parts do not remain at dangerous voltages, reducing shock and fire risk.