# 36. Electric storage heaters

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## Electric Storage Heaters

We now know that different materials store different amounts of heat energy. It is the specific heat capacity of a material that tells us how much energy it can store for a certain temperature rise.

Electric storage heaters are usually turned on at night when the cost of electricity is cheaper than in the day. During the night they transfer electrical energy into heat energy to warm materials such as oil, water or concrete, depending on the type of heater.

During the day, the heater is turned off. However, the hot material inside the storage heater gradually cools, releasing its heat energy to the room around it.

In this flashcard we have two electric storage radiators, one with oil as the heated material and the other with the same mass of water.

If they are both heated to the same temperature during the night, which one will be able to store the most heat energy?

We need to compare the specific heat capacity of oil (1970 J/kg°C) with that of water (4200 J/kg°C). This means that oil needs 1970 Joules to raise one kilogram of oil by one degree Celsius. However, water needs 4200 Joules to raise the temperature of one kilogram by one degree.

A lot more heat energy is needed by the water filled storage heater for each 1°C rise, and so it can store a great deal more energy than the oil-filled radiator.

GCSE Physics Keywords: Specific heat capacity, Heat energy, Temperature rise, Mass, Electric storage heater

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