Current electricity II — 10-topic bundle

Imagine you have a pump lifting water to a higher level. The e.m.f. is like the total energy the pump gives to each liter of water, including any energy lost due to friction inside the pump itself.

Mathematically, it's defined as:
$e.m.f. = \frac{\text{Energy supplied (W)}}{\text{Charge moved (Q)}}$

Since energy is measured in Joules (J) and charge in Coulombs (C), the unit for e.m.f. is Joules per Coulomb (J/C), which is equivalent to a Volt (V).

Key Concepts:
* Sinusoidal Waveforms: AC voltage and current typically follow a sine wave pattern. You'll need to understand terms like peak voltage ($V_p$), RMS voltage ($V_{RMS}$), frequency ($f$), period ($T$), and phase angle ($\phi$). Remember, $V_{RMS} = V_p / \sqrt{2}$. This RMS value is what most multimeters show and what's used for power calculations.
* Phasors: Since AC quantities are constantly changing, it's hard to represent them with single numbers. Phasors are rotating vectors that represent sinusoidal quantities. Their length indicates amplitude (usually RMS value), and their angle indicates phase. They simplify AC circuit analysis by turning time-varying functions into static vectors that can be added and subtracted graphically or using complex numbers.

When we talk about a power source like a battery, we often think of its "voltage." But there are actually two important voltages: EMF and terminal voltage.

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When we talk about a cell or battery, we often refer to its electromotive force (e.m.f.), which is the total electrical energy provided by the cell per unit charge. Think of e.m.f. as the maximum potential difference the cell could provide when no current is being drawn from it (i.e., in an open circuit).

An operational amplifier, or op-amp, is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. They're called "operational" because they used to be used to perform mathematical operations in analog computers.

When we talk about a power source like a battery or a generator, we often think of it as having a fixed voltage. However, in reality, every power source has some inherent resistance inside it. This is called internal resistance, and it affects the voltage you actually get out of the source.

Let's break down the key terms:

EMF is the total energy per unit charge that a power source can provide. Think of it as the "strength" of the source when it's just sitting there, not powering anything. It's the maximum potential difference across its terminals when no current is flowing (i.e., in an open circuit). EMF is measured in Volts (V).