Think along the lines of Compound Interest (but in reverse)

For example- Asset of 100 depreciating by 20% p.a

On Straight Line

Year1 Asset 100 Depreciation 20

Year2 Asset 80 Depreciation 20

Year3 Asset 60 Depreciation 20

Year4 Asset 40 Depreciation 20

Year5 Asset 20 Depreciation 20

Year6 Asset 0

On Diminishing Balance

Year1 Asset 100 Depreciation 20

Year2 Asset 80 Depreciation 16

Year3 Asset 64 Depreciation 12.8

Year4 Asset 51.2 Depreciation 10.24

Year5 Asset 40.96 Depreciation 8.192

Year6 Asset 32.77

.... and so on until the asset tends to 0 (will never technically reach 0)

Depreciation expense is neither an asset or liability. It is an expense.

Depreciating asset is that asset which is utilizing by business in generating revenue and cost of asset is allocating to income statement through depreciation.

Book Value is the difference between the cost of an asset and the accumulated depreciation of that asset.

When the asset is disposed of the Accumulated Depreciation is subtracted from the cost of the asset.

Journal Entries:

If Sold at a Profit:

Dr Accumulated Depreciation (All Depreciation)

Dr Bank/ Recievable (Amount received for Asset)

Cr Asset (Carrying Value on Balance Sheet)

Cr Profit on Asset Disposal (Balancing Figure)

If Sold at a Loss:

Dr Accumulated Depreciation (All Depreciation)

Dr Bank/ Recievable (Amount received for Asset)

Dr Loss on Asset Disposal (Balancing Figure)

Cr Asset (Carrying Value on Balance Sheet)

Please note there may also be current year depreciation