Free & Cheap this week

FOOTPRINTS OF MEMORY: This exhibition at Amnesty International’s Shoreditch offices is raising awareness of people — particularly students — who have disappeared in Mexico in recent years. It features 40 pairs of shoes worn by people when they were searching for their family members, and messages for the missing. Amnesty International (25 New Inn Yard, EC2A 3EA), free, just turn up, 20-31 March, 9am-6pm

#IAMYEZIDI: This photography exhibition portrays the hardships faced by Yezidi women in Iraq. Includes stories of women who have escaped slavery and rescued their children from ISIS captivity.Lacey Contemporary Gallery, free, just turn up, 21-26 March

THE BEST IN PHOTOGRAPHY: We always look forward to the Deutsche Börse Photography Prize as the benchmark of photography as art. The finalists’ styles change dramatically every year, and this annual exhibition has included many impressive winners in the past. The Photographers’ Gallery, £4 (free before noon), just turn up, until 11 June

ELECTRICITY: Been to Wellcome Collection’s Electricity exhibition yet? It charts humanity’s history of believing God created lightning, to the futuristic Masdar city in Abu Dhabi, via experiments with twitching frogs legs and the construction of the National Grid. Wellcome Collection, free, just turn up, until 25 June