Grade 10 electricity – Cells and Batteries Quiz

A cell produces electrical energy by chemical reactions between its electrodes and electrolyte; instruments measure current and other devices store or block energy.

A battery is simply an assembly of two or more cells connected in series or parallel to achieve higher voltage or capacity.

In common galvanic cells (e.g., Daniell), oxidation occurs at the zinc anode, releasing electrons so the anode is negative.

Electrolytes conduct ions (not electrons) inside the cell, allowing the chemical reactions to continue and complete the circuit.

A standard alkaline AA cell has a nominal voltage of about 1.5 V when fresh.

Most vehicle lead-acid batteries are 12 V, made of six 2 V cells connected in series.

Rechargeable batteries allow the discharge reactions to be reversed by applying an external voltage, restoring reactants for reuse.

In series connection, the EMFs of cells add, so two 1.5 V cells give about 3.0 V.

Parallel connection keeps the voltage equal to one cell but combines capacities, giving longer run time at the same voltage.

V_terminal = emf - I * r_int, so higher current or internal resistance causes a larger voltage drop inside the cell.

The terminal voltage is the electromotive force minus the voltage drop across the internal resistance (I times r).

Series addition gives 1.5 V + 1.5 V = 3.0 V for the pair.

Parallel connection keeps the voltage the same as one cell but increases the available current and capacity.

Lead-acid batteries provide the high currents needed for engine cranking and are standard in vehicles.

Alkaline cells are typically primary cells and are not designed to be recharged safely.

In a discharging cell the anode undergoes oxidation, releasing electrons that flow through the external circuit.

A voltmeter measures potential difference with a very high internal resistance so it draws negligible current.

Parallel cells increase total capacity (mAh) so the torch runs longer at the same voltage.

mAh indicates the charge stored: for example, 2000 mAh means 2000 mA for one hour or 1000 mA for two hours, approximately.

A short circuit bypasses the load, allowing huge current limited only by internal resistance, which produces heat and can damage or ignite the battery.

Cool, dry storage slows self-discharge; preventing terminal contact avoids accidental short circuits and damage.

High temperatures accelerate chemical degradation, reducing useful lifespan and sometimes causing dangerous failure.

Lead-acid batteries are hazardous; they should be recycled through authorised centres to recover lead and prevent pollution.

The zinc rod loses electrons (oxidation) and the copper ion gains electrons (reduction) in the Daniell cell.

High internal resistance causes a large voltage drop when current flows, so voltage falls quickly under load.

A cell converts chemical reactions between its electrodes and electrolyte into electrical energy; this is the basic unit of batteries used in torches, radios and phones.

A battery is formed when two or more electrochemical cells are connected so their voltages or capacities combine to provide the required power.

Oxidation (loss of electrons) occurs at the anode; in a galvanic cell the anode is the negative electrode supplying electrons to the external circuit.

The salt bridge allows ions to move: anions flow to the anode compartment to balance positive charge, while cations flow toward the cathode to balance negative charge, completing the circuit.

Standard primary dry cells such as AA, AAA, C and D are about 1.5 V each when new; multiple cells are combined for higher voltages.

Primary cells (e.g., zinc–carbon, alkaline) are intended for one-time use and disposal, whereas secondary cells (e.g., lead-acid, NiMH) can be recharged by reversing the chemical reactions.

In series, voltages add while the capacity in ampere-hours remains equal to a single cell's capacity; series is used when more voltage is needed.

Parallel connection keeps the voltage equal to one cell but adds capacities (Ah), giving longer run time for devices at the same voltage.

EMF is the maximum potential difference a cell can provide; when no current flows (open circuit) the terminal voltage equals the EMF.

When current flows, voltage is lost across the internal resistance (V = Ir), so terminal voltage under load is EMF minus this drop, causing reduced voltage to the device.

Car batteries are lead-acid batteries designed to deliver high current for starting engines and are rechargeable via the vehicle's alternator.

Batteries often contain lead, cadmium, mercury or other harmful substances; proper collection and recycling prevent environmental contamination and allow material recovery.

Alkaline cells generally deliver more energy and last longer in many devices compared with zinc–carbon cells, and have better shelf life when unused.

Mixing different types or capacities can cause uneven charging/discharging, leading to overheating, reduced performance or even leakage and fire; matched cells are safer.

Battery capacity is given in ampere-hours (Ah) or milliampere-hours (mAh), which indicate the current a battery can supply over time (e.g., 1 Ah = 1 A for 1 hour).

In series, voltages add: 1.5 V + 1.5 V = 3.0 V, which is the typical voltage for many household torch designs.

Oxidation at the anode releases electrons that travel through the external circuit to the cathode where reduction occurs.

The electrolyte contains ions that move inside the cell to maintain charge balance as electrons flow through the external circuit, enabling the cell's operation.

Galvanic cells generate electricity from spontaneous redox reactions where one substance is oxidized and another is reduced, releasing electrical energy.

As discharge proceeds, the concentrations of reactants change and internal resistance may increase, causing the terminal voltage to drop gradually.

Charging lead-acid batteries can release hydrogen gas which is explosive; keep sparks and flames away and work in a ventilated area.

Starting an engine requires a large current for a short time; car batteries are rated for cranking amps to indicate their ability to deliver that surge.

A short circuit allows excessive current limited only by internal resistance; this generates heat, can rupture the cell or cause leakage, fire or explosion.

The Daniell cell uses a zinc anode in zinc sulfate and a copper cathode in copper sulfate, with a salt bridge; it is a classic example of a galvanic cell.

Lithium-ion cells store large amounts of energy for their size, making them common in phones, but they need correct chargers and protection circuits to prevent overheating and failure.