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# Current Electricity ## 9.1 Sources of Direct Current We are familiar with cells used in a torch to light up a bulb. These cells are the source of direct current (abbreviated as d.c.), which lights up the bulb. The current flows from the positive terminal of the cell to the negative terminal thr...

# Current Electricity ## 9.1 Sources of Direct Current We are familiar with cells used in a torch to light up a bulb. These cells are the source of direct current (abbreviated as d.c.), which lights up the bulb. The current flows from the positive terminal of the cell to the negative terminal through the bulb. The magnitude of the current given by a cell remains constant for a sufficiently long time. When the cell gets discharged, it stops giving current and becomes useless. Direct current (d.c.) is a current of constant magnitude flowing in one direction. **Diagram:** A simple diagram of a dry cell is shown. It depicts a dry cell with labeled components: Brass cap, Dry cell, Zinc, and Bulb. **Types of Cells:** Cells are categorized into two kinds: 1. **Primary cells:** These cells produce current as a result of irreversible chemical reactions. Once the chemical energy is used, the cell is discarded, and these cells cannot be recharged. Examples include the Leclanche cell and dry cell. 2. **Secondary cells or accumulators:** These cells are rechargeable and can be used repeatedly. **Structure of a Cell:** A cell consists of a vessel containing two electrodes which are placed or immersed in a solution (or jelly), called the electrolyte. **Key Concepts:** * **Electrodes:** The conducting rods within the cell. * **Electrolyte:** The solution or jelly within the cell. * **Chemical energy:** Changed to electrical energy when a cell sends current.