Coolant: A mixture of antifreeze and water which is circulated the engine to cool the same.

Controller: Electronic power control device to regulate the d.c. voltage supplied by the batteries to the d.c. motor; usually done by chopping the d.c. current up to a different duty cycle, which is called pulse width modulation and is done at a very high frequency.

Connecting rod: It converts the linear motion of the piston into the rotary motion of the crankshaft. Its small end is connected to the piston and big and to the crankshaft.

Condenser: An electrical device which acts to store electrical charge at the break of circuit and supplies the same during the make period of circuit.

Compression ratio: It is the ratio of the cylinder volume above the piston at BDC to the volume above the piston at TDC.

Common rail injection: A diesel engine fuel supply system in which a single pump delivers fuel at very high pressure, say, 1400 bar to a common reservoir from which supply goes to various injectors.

Combustion chamber: The small space in the engine cylinder head and/or piston into which air-fuel mixture (in petrol engines) or air (in diesel engines) is compressed and is burnt.

Compressed Natural Gas (CNG): Alternative fuel consisting of natural gas compressed from 160 to 200 bar.

Clearance volume: The volume of the engine cylinder (including the combustion chamber volume) above the piston when it is in the TDC position.

Circuit breaker: A switch which protects an electrical circuit from overload by opening the circuit when the current flow exceeds a pre-determined level.

Choke: A butterfly valve fitted at the top of the air horn of a carburettor to provide rich mixture during starting of engine.

Check engine light: The malfunction indicator light that the vehicle's on-board computer illuminates when it senses a fault in the engine.

Cetane rating: A measure of the auto-ignition value of diesel fuel. It is defined as the percentage of cetane in a mixture of cetane and alpha methylnaphthalene, which has the same diesel knock characteristics as fuel under test.

Cetane: n-hexadecane (C16H34) is a straight chain paraffin, which is assigned the cetane number of 100.

Catalytic converter: It is a cylindrical unit installed into the exhaust system of a vehicle, between the exhaust manifold and the silencer. Due to the presence of catalyst in the converter toxic gases in the exhaust, i.e., CO, HC and NOx are converted into harmless CO2, H2O and N2. Commonly used catalysts are platinum and rodium. A three way catalytic converter can be used in case of a petrol engine only. In diesel engines, only a two-way converter is used.